U.S. President Barack Obama waves as he arrives to take part in the G20 Summit in St. Petersburg, September 5, 2013. REUTERS/Alexander Demianchuk (RUSSIA - Tags: POLITICS BUSINESS) 

U.S. President Barack Obama arrives in St. Petersburg, Russia to attend the G20 Summit September 5, 2013. REUTERS/Kevin Lamarque (RUSSIA - Tags: POLITICS BUSINESS) 

U.S. President Barack Obama sits inside a car upon his arrival for the G20 Summit in St. Petersburg September 5, 2013. REUTERS/Alexander Demianchuk (RUSSIA - Tags: POLITICS)

An interior view of the main press centre of the G20 summit is seen in Strelna near St. Petersburg September 4, 2013. The Group of 20 cut its teeth in the global financial crisis of 2009, achieving unprecedented cooperation between developed and emerging nations to stave off economic collapse which has not been matched since. REUTERS/Alexander Demianchuk (RUSSIA - Tags: MEDIA BUSINESS POLITICS) 

A journalist boards a high-speed vessel to get from the sea port to Konstantinovsky (Konstantin) Palace, the main venue of the G20 Summit, in St. Petersburg September 4, 2013. The Group of 20 cut its teeth in the global financial crisis of 2009, achieving unprecedented cooperation between developed and emerging nations to stave off economic collapse which has not been matched since. REUTERS/Alexander Demianchuk (RUSSIA - Tags: MEDIA BUSINESS POLITICS TRANSPORT) 

Sailors stand near temporary signs for the G20 summit at the sea port in St. Petersburg September 4, 2013. The Group of 20 cut its teeth in the global financial crisis of 2009, achieving unprecedented cooperation between developed and emerging nations to stave off economic collapse which has not been matched since. REUTERS/Alexander Demianchuk (RUSSIA - Tags: POLITICS BUSINESS)