Russian President Vladimir Putin says his country may agree to strikes on Syria, if there's proof Assad's regime used chemical weapons.
He was speaking as American senators agreed a draft resolution on military action, to be voted on next week.
The agreement states that any strikes would have to take place within a 60 day time limit and that there will be no US soldiers on the ground in combat.
Russian premier Mr. Putin has warned America off taking what he calls 'one-sided action', insisting the West must get approval from the UN before taking any action.
Mr. Putin has warned the US over 'aggression' against the US, in an interview with the Associated Press:
The two are due to meet at the G20 summit in St. Petersburg, Russia this week.
Speaking about icy relations between them, Vladamir Putin said neither leader had been elected to be pleasant to the other, adding that both of them 'are human' and sometimes get vexed with each other. However, he's insisted that there is still a good basis between the two countries for finding joint international solutions.
Chemical attack
President Putin has said he was shocked by images of the victims of a chemical attack near Damascus last month, but has suggested that the footage could be 'a compilation by these very rebels who are connected to al Qaeda'.
The US meanwhile says it has proof that the Assad regime was behind sarin gas attacks that it believes killed at least 1,429 people on the outskirts of Damascus on August 21.
Other players wait
France is set to hold an emergency parliamentary debate later over whether it should join military action in Syria.
The speaker of Syria's parliament, Mohammad Jihad al Lahham, has written to French MPs urging them to work towards a diplomatic solution to the crisis.
President Francois Hollande has backed strikes but says he will wait until the result of the US congressional vote.
British MPs rejected military action during a vote in Parliament last week.
United Nations leader Ban Ki-moon has stopped short of opposing strikes but told Western powers that it is possible they could make the situation worse.
"We must consider the impact of any punitive measure on efforts to prevent further bloodshed and facilitate the political resolution of the conflict," he said.
