The US Senate Foreign Relations Committee on Wednesday approved a resolution authorising the use of military force in Syria by 10 votes to seven.
A vote on the resolution will now be held in the full Senate next week. Congress will also vote next week.
The proposal allows the use of force in Syria for 60 days with the possibility to extend it for 30 days. It prevents the use of US troops on the ground.
Secretary of State John Kerry told the committee a failure to act would encourage extremism. He said any military strike would "degrade" Syria's ability to use chemical weapons but would not involve boots on the ground.
However, the BBC reports the bill's ultimate fate in the Senate is unclear. And the House of Representatives must also approve the measure next week.
So far, only 21 senators have said they support or are likely to support the resolution, according to a tally by ABC News.
Thirteen have said they oppose or are likely to oppose it, while 66 votes are undecided or unknown.
The government of President Bashar al-Assad is accused of using chemical weapons against civilians on 21 August on the outskirts of Damascus.
The United States says the death toll was 1429 and says all the evidence implicates government forces.
Query by Putin
President Vladimir Putin of Russia says the United States Congress has no right to approve the use of force against Syria without a decision from the United Nations Security Council.
At a meeting of the presidential council for human rights in the Kremlin, Mr Putin said any action outside a Security Council mandate, except self-defence, was an act of aggression. He said that was inadmissable in principle.
United States President Barack Obama said on Wednesday the credibility of the United States and the international community was on the line over their response to the use chemical weapons in Syria.
Speaking in Sweden, he said the world should stick to its own "red line" against the use of chemical weapons.
Debate in France
The BBC reports France held an extraordinary debate in the National Assembly, though deputies will not vote on the matter.
Prime Minister Jean-Marc Ayrault stressed the need to take action together, saying: "Faced with barbarism, doing nothing is not an option."
He said it was "France's honour, France's duty" to act and that President Francois Hollande was continuing efforts to bring together a coalition.
"What message would this send to other regimes, and I am thinking like you of Iran and North Korea? The message would be clear: You can continue," he added.
The British parliament voted last month against military intervention in Syria.