The U.S.-led push to bomb Syria is overshadowing the G-20 economic summit in St. Petersburg, Russia, where world leaders remain divided on whether to support the attack. President Obama is pressing his plan to strike Syria in retaliation for a chemical attack last month in Ghouta during which the administration claims the Syrian government killed more than 1,400 people. On Thursday, Britain bolstered those reports, saying new lab tests had confirmed the use of sarin nerve gas. But the two-day summit is being hosted by Russian President Vladimir Putin, a key Syrian ally who rejects the U.S. claims.