Just hours before President Barack Obama was set to arrive at the G20 Summit, Russian president Vladimir Putin slammed the U.S. and Secretary of State John Kerry over recent testimony on the civil war in Syria with Putin calling him a liar.

"I've watched debates in Congress. The congressman asked Mr. Kerry, 'Is there al-Qaeda? People say they've gotten stronger.' He says, 'No, I say officially they're not there.' The main combat unit, the so-called al-Nusra, is a unit of al-Qaeda. They (the Americans) know about this. This was very unpleasant and surprising for me. We talk to them (the Americans) and we assume they are decent people, but he is lying and he knows that he is lying. This is sad."

During the remarks, Putin also restated his country's position, saying that any use of military force against Syria without U.N. approval would be considered an 'act of aggression.'

Watch the remarks and reaction from the U.S. above.

Just moments ago, President Obama met and greeted Putin. Watch the handshake in the video below.