Jennifer Williams, special adviser for Europe and Russia in the Office of U.S. Vice President Mike Pence arrives on Capitol Hill for a closed-door hearing in Washington, U.S., November 7, 2019. REUTERS/Tom Brenner

Jennifer Williams, special adviser for Europe and Russia in the Office of U.S. Vice President Mike Pence arrives on Capitol Hill for a closed-door hearing in Washington, U.S., November 7, 2019. REUTERS/Tom Brenner

Jennifer Williams, special adviser for Europe and Russia in the Office of U.S. Vice President Mike Pence arrives on Capitol Hill for a closed-door hearing in Washington, U.S., November 7, 2019. REUTERS/Tom Brenner

Acting U.S. ambassador to Ukraine Bill Taylor arrives on Capitol Hill before a closed-door hearing with members of Congress in Washington, U.S., October 22, 2019. REUTERS/Tom Brenner

Acting U.S. ambassador to Ukraine Bill Taylor arrives to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 22, 2019. REUTERS/Carlos Jasso

Acting U.S. ambassador to Ukraine Bill Taylor arrives on Capitol Hill before a closed-door hearing with members of Congress in Washington, U.S., October 22, 2019. REUTERS/Tom Brenner

Acting U.S. ambassador to Ukraine Bill Taylor is pursued by members of the media as he arrives to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 22, 2019. REUTERS/Carlos Jasso

Former U.S. ambassador to Ukraine Marie Yovanovitch arrives to testify in the U.S. House of Representatives impeachment inquiry into U.S. President Trump on Capitol Hill in Washington, U.S., October 11, 2019. REUTERS/Jonathan Ernst TPX IMAGES OF THE DAY

Former U.S. ambassador to Ukraine Marie Yovanovitch departs after testifying in the U.S. House of Representatives impeachment inquiry into U.S. President Trump on Capitol Hill in Washington, U.S., October 11, 2019. REUTERS/Jonathan Ernst

Former U.S. ambassador to Ukraine Marie Yovanovitch arrives to testify in the U.S. House of Representatives impeachment inquiry into U.S. President Trump on Capitol Hill in Washington, U.S., October 11, 2019. REUTERS/Jonathan Ernst

Former U.S. ambassador to Ukraine Marie Yovanovitch leaves after testifying in the U.S. House of Representatives impeachment inquiry into U.S. President Trump on Capitol Hill in Washington, U.S, October 11, 2019. REUTERS/Carlos Jasso

U.S. Ambassador to the European Union Gordon Sondland arrives to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 28, 2019. REUTERS/Erin Scott

U.S. Ambassador to the European Union Gordon Sondland departs after testifying at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 28, 2019. REUTERS/Siphiwe Sibeko

U.S. Ambassador to the European Union Gordon Sondland arrives on Capitol Hill before testifying to congress behind closed doors, as part of the impeachment inquiry led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees, in Washington, U.S., October 17, 2019. REUTERS/Tom Brenner

Fiona Hill, former senior director for European and Russian affairs on the National Security Council, departs after testifying in the U.S. House of Representatives impeachment inquiry into U.S. President Trump on Capitol Hill in Washington, U.S., October 14, 2019. REUTERS/Carlos Jasso

Fiona Hill, former senior director for European and Russian affairs on the National Security Council, departs after testifying in the U.S. House of Representatives impeachment inquiry into U.S. President Trump on Capitol Hill in Washington, U.S., October 14, 2019. REUTERS/Carlos Jasso

Fiona Hill, former senior director for European and Russian affairs on the National Security Council, arrives to review her previous testimony in the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., November 4, 2019. REUTERS/Leah Millis

Fiona Hill, former senior director for European and Russian affairs on the National Security Council, arrives to review her previous testimony in the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., November 4, 2019. REUTERS/Leah Millis

Fiona Hill, former senior director for European and Russian affairs on the National Security Council, arrives to review her previous testimony in the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., November 4, 2019. REUTERS/Leah Millis

Fiona Hill, former senior director for European and Russian affairs on the National Security Council, leaves after reviewing her previous testimony in the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., November 4, 2019. REUTERS/Leah Millis

Fiona Hill leaves the Capitol building after giving a full day of testimony during the ongoing House of Representatives impeachment inquiry into U.S. President Trump on Capitol Hill in Washington, U.S., October 14, 2019. REUTERS/Leah Millis TPX IMAGES OF THE DAY

Lt. Col. Alexander Vindman, director for European Affairs at the National Security Council, arrives to testify as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 29, 2019. REUTERS/Siphiwe Sibeko

Lt. Col. Alexander Vindman, director for European Affairs at the National Security Council, arrives to testify as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 29, 2019. REUTERS/Siphiwe Sibeko

Lt. Col. Alexander Vindman, director for European Affairs at the National Security Council, arrives to testify as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 29, 2019. REUTERS/Erin Scott

Kurt Volker, U.S. President Donald Trump's former envoy to Ukraine, arrives to be interviewed by staff for three House of Representatives committees as part of the impeachment inquiry into the president's dealings with Ukraine, at the U.S. Capitol in Washington, U.S. October 3, 2019. REUTERS/Jonathan Ernst

Kurt Volker, U.S. President Donald Trump's former envoy to Ukraine, arrives to participate in a closed-door deposition as part of the Democratic-led U.S. House of Representatives impeachment inquiry into U.S. President Donald Trump on Capitol Hill in Washington, U.S., October 16, 2019. REUTERS/Carlos Jasso

Kurt Volker, U.S. President Donald Trump's former envoy to Ukraine, arrives to be interviewed by staff for three House of Representatives committees as part of the impeachment inquiry into the president's dealings with Ukraine, at the U.S. Capitol in Washington, U.S. October 3, 2019. REUTERS/Jonathan Ernst

Deputy Assistant Secretary of Defense Laura Cooper, the Pentagon official in charge of Ukraine and Russia policy, arrives to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 23, 2019. REUTERS/Carlos Jasso?

Deputy Assistant Secretary of Defense Laura Cooper, the Pentagon official in charge of Ukraine and Russia policy, arrives to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 23, 2019. REUTERS/Carlos Jasso?

U.S. House Republicans speak to reporters after Deputy Assistant Secretary of Defense Laura Cooper arrived to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S. October 23, 2019. REUTERS/Carlos Jasso TPX IMAGES OF THE DAY

Deputy Assistant Secretary of Defense Laura Cooper, the Pentagon official in charge of Ukraine and Russia policy, arrives to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 23, 2019. REUTERS/Carlos Jasso?

Deputy Assistant Secretary of Defense Laura Cooper, the Pentagon official in charge of Ukraine and Russia policy, arrives behind U.S. Capitol Police officers and an aide or attorney to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 23, 2019. REUTERS/Carlos Jasso? TPX IMAGES OF THE DAY

Timothy Morrison, special assistant to the president and senior director for Europe and Russia at the National Security Council, arrives for a closed-door deposition as part of the impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 31, 2019. REUTERS/Joshua Roberts

Timothy Morrison, special assistant to the President and senior director for Europe and Russia at the National Security Council, arrives on Capitol Hill to testify in private before members of congress, in Washington, U.S., October 31, 2019 REUTERS/Tom Brenner

Timothy Morrison, special assistant to the President and senior director for Europe and Russia at the National Security Council, arrives on Capitol Hill to testify in private before members of congress, in Washington, U.S., October 31, 2019 REUTERS/Tom Brenner

Timothy Morrison, special assistant to the president and senior director for Europe and Russia at the National Security Council, returns to testify at a closed-door deposition as part of the impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., November 6, 2019. REUTERS/Siphiwe Sibeko

George Kent, deputy assistant secretary of state for Europe and Eurasian Affairs, arrives to testify at a closed-door deposition as part of the Democratic-led U.S. House of Representatives impeachment inquiry into U.S. President Donald Trump on Capitol Hill in Washington, U.S., October 15, 2019. REUTERS/Carlos Jasso

George Kent, deputy assistant secretary of state for Europe and Eurasian Affairs, arrives to testify at a closed-door deposition as part of the Democratic-led U.S. House of Representatives impeachment inquiry into U.S. President Donald Trump on Capitol Hill in Washington, U.S., October 15, 2019. REUTERS/Carlos Jasso

U.S. foreign service officer Catherine Croft, who once served as a deputy to then-Special Envoy for Ukraine Kurt Volker, arrives to testify as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 30, 2019. REUTERS/Siphiwe Sibeko

U.S. foreign service officer Catherine Croft, who once served as a deputy to then-Special Envoy for Ukraine Kurt Volker, arrives to testify as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 30, 2019. REUTERS/Siphiwe Sibeko

David Hale, Under Secretary of State for Political Affairs, arrives for a closed-door deposition as part of the impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., November 6, 2019. REUTERS/Joshua Roberts

David Hale, Under Secretary of State for Political Affairs, arrives for a closed-door deposition as part of the impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., November 6, 2019. REUTERS/Joshua Roberts

David Hale, Under Secretary of State for Political Affairs, arrives for a closed-door deposition as part of the impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., November 6, 2019. REUTERS/Joshua Roberts

Philip Reeker, U.S. acting assistant secretary of state for European and Eurasian Affairs, arrives to testify in impeachment inquiry against U.S. President Donald Trump, in Washington, U.S., October 26, 2019. REUTERS/Siphiwe Sibeko

Christopher Anderson, who once served as a deputy to then Special Envoy for Ukraine Kurt Volker, arrives to testify as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 30, 2019. REUTERS/Siphiwe Sibeko

A draft of a U.S. House of Representatives resolution formally laying out the next steps in the Democratic impeachment inquiry of President Donald Trump, authorizing public committee hearings and the public release of transcripts of closed-door depositions, is seen after its release on Capitol Hill in Washington, October 29, 2019. REUTERS/Jim Bourg

A draft of a U.S. House of Representatives resolution formally laying out the next steps in the Democratic impeachment inquiry of President Donald Trump, authorizing public committee hearings and the public release of transcripts of closed-door depositions, is seen after its release on Capitol Hill in Washington, October 29, 2019. REUTERS/Jim Bourg

U.S. House Intelligence Committee Chair Rep. Adam Schiff (D-CA) leaves a hearing with Lt. Col. Alexander Vindman, director for European Affairs at the National Security Council, as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 29, 2019. REUTERS/Erin Scott TPX IMAGES OF THE DAY

Congressman Mark Meadows (R-NC) looks back at reporters as he enters a secure area as Deputy Assistant Secretary of Defense Laura Cooper testifies in a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Donald Trump on Capitol Hill in Washington, U.S., October 23, 2019. REUTERS/Yuri Gripas TPX IMAGES OF THE DAY

House Minority Whip Steve Scalise (R-LA) with other Republican congressmen speaks to the media outside a secure area as Deputy Assistant Secretary of Defense Laura Cooper testifies in a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Donald Trump on Capitol Hill in Washington, U.S., October 23, 2019. REUTERS/Yuri Gripas