Burundi's President Pierre Nkurunziza kicks the ball during a soccer game with his friends in Bujumbura, Burundi, May 20, 2015. Nkurunziza on Wednesday urged more than 110,000 people who have fled political violence in the last month to return home, saying "99.9 percent" of the impoverished east African nation was peaceful and safe. REUTERS/Goran Tomasevic 

Former Massachusetts Governor and two-time presidential candidate Mitt Romney (R) fights five-time heavyweight champion Evander Holyfield during their boxing match in Salt Lake City, Utah May 15, 2015. The two boxed to benefit the medical charity CharityVision. REUTERS/Jim Urquhart TPX IMAGES OF THE DAY

U.S. President Barack Obama gets hit on the head by a rebound while playing basketball, an exercise activity during the annual Easter Egg Roll at the White House in Washington April 6, 2015. REUTERS/Jonathan Ernst 

U.S. President Barack Obama plays table tennis against students with British Prime Minister David Cameron at the Globe Academy in London May 24, 2011. REUTERS/Larry Downing (BRITAIN - Tags: POLITICS SPORT TABLE TENNIS IMAGES OF THE DAY) 

France's President Francois Hollande (L) prepares to shoot an arrow during a visit to meet members of the French team for the London Olympics 2012 at the training headquarters of INSEP (National Institute for Sport and Physical Education) in Paris July 16, 2012. REUTERS/Charles Platiau (FRANCE - Tags: SPORT ARCHERY POLITICS OLYMPICS) 

U.S. Secretary of State John Kerry kicks a soccer ball around during an airplane refuelling stop at Sal Island, Cape Verde, enroute to Washington, DC, May 5, 2014. REUTERS/Saul Loeb/Pool (CAPE VERDE - Tags: POLITICS TPX IMAGES OF THE DAY) 

U.S. Secretary of State John Kerry (L) cycles past the Olympic Museum in Lausanne, March 16, 2015. Kerry and Iranian counterpart Mohammad Javad Zarif held four hours of nuclear talks on Monday in the Swiss city of Lausanne before the Iranian delegation headed to Brussels for meetings with European ministers. REUTERS/Denis Balibouse (SWITZERLAND - Tags: POLITICS SPORT TPX IMAGES OF THE DAY)

Britain's Prime Minister David Cameron (2nd R) jogs with British forces at Camp Bastion in Helmand Province, Afghanistan June 11, 2010. Cameron told troops on Friday they were not in Afghanistan for a "dreamy idea" or to build a model society, and pledged they would leave once Afghans could defend themselves. On his first trip as prime minister to meet British troops in southern Afghanistan, Cameron said the new coalition he heads had a clear mission -- defending Britain's national security from the threat of attack by al Qaeda. REUTERS/Stefan Rousseau/POOL (AFGHANISTAN - Tags: CIVIL UNREST MILITARY POLITICS) 

U.S. President Barack Obama shoots pool during a stop in a bar in Denver July 8, 2014. Obama will speak about the economy at an event in Denver tomorrow.
REUTERS/Kevin Lamarque (UNITED STATES - Tags: POLITICS) 

Japan's Prime Minister Shinzo Abe heads the ball during a meeting with Brazilian soccer players in Brasilia, August 1, 2014. REUTERS/Ueslei Marcelino (BRAZIL - Tags: POLITICS SPORT SOCCER TPX IMAGES OF THE DAY) 

U.S. First Lady Michelle Obama plays mini-tennis during a "Let's Move!" faith and communities physical activity at Disney World's ESPN Wide World of Sports in Orlando, Florida February 11, 2012. The first lady is concluding a three-day trip to mark the second anniversary of her "Let's Move" initiative.
REUTERS/Kevin Lamarque (UNITED STATES - Tags: HEALTH POLITICS TPX IMAGES OF THE DAY) 

China's Vice-President Xi Jinping kicks a football during a visit to Croke Park in Dublin, Ireland February 19, 2012. REUTERS/David Moir (IRELAND - Tags: POLITICS SPORT SOCCER TPX IMAGES OF THE DAY) 

French Socialist Party first secretary Francois Hollande chases the ball during a charity soccer match aimed at raising funds for the France-Alzheimer association at the Charlety stadium in Paris May 20, 2008. REUTERS/Charles Platiau (FRANCE) 

Chinese Premier Wen Jiabao (C) practises tai chi with local residents at a park in Macau November 14, 2010. Wen is on a two-day visit to take part in the opening ceremony of the third Ministerial Conference of the Forum for Economic and Trade Cooperation between China and Portuguese-speaking Countries. REUTERS/Tyrone Siu (CHINA - Tags: POLITICS SPORT ODDLY IMAGES OF THE DAY) 

Conservative leader and Canada's Prime Minister Stephen Harper plays ball hockey during a campaign stop in Ottawa April 3, 2011. Canadians will head to the polls in a federal election May 2. REUTERS/Chris Wattie (CANADA - Tags: POLITICS ELECTIONS) 

London Mayor Boris Johnson takes part in a charity game of tennis at the Queen's Club in west London June 16, 2013. REUTERS/Eddie Keogh (BRITAIN - Tags: SPORT TENNIS POLITICS SOCIETY ENTERTAINMENT TPX IMAGES OF THE DAY) 

U.S. President Barack Obama reacts after missing a putt on the first green at the Farm Neck Golf Club at Oak Bluffs on Martha's Vineyard, August 11, 2013. REUTERS/Larry Downing (UNITED STATES - Tags: POLITICS SPORT GOLF) 

Former French President Nicolas Sarkozy jogs in Paris, November 28, 2012. France's main conservative UMP party edged closer to a formal split on Wednesday as the winner of a leadership contest broke a fragile truce between him and his rival brokered hours earlier by former president Nicolas Sarkozy. REUTERS/Benoit Tessier (FRANCE - Tags: POLITICS SPORT TPX IMAGES OF THE DAY) 

New Jersey Governor Chris Christie plays table tennis following a news conference at the Boys and Girls Club of Newark Clubhouse in Newark, New Jersey January 27, 2014. The event was held to announce the NFL Foundation's grant to the New York/New Jersey Super Bowl Host Committee's Snowflake Youth Foundation to fund charitable projects throughout New York and New Jersey. REUTERS/Andrew Kelly (UNITED STATES - Tags: POLITICS SPORT TABLE TENNIS TPX IMAGES OF THE DAY)