The US House of Representatives has approved President Barack Obama's plan to arm and train Syrian rebels.
The move is part of America's planned war against Islamic State (IS), the jihadist group that controls parts of Syria and Iraq.
The BBC's Tom Esslemont reports that the vote was expected to pass easily.
"Republicans, who control the House, generally support President Obama's strategy to defeat and degrade Islamic State but the more hawkish among them feel the plan falls short," he said.
"They argue that the president should consider sending US combat troops to Syria and Iraq - something he has said he is not prepared to do."
Mr Esslemont said some lawmakers from both parties were sceptical that the Syrian rebels were up to the job.
"At a Senate committee hearing, they pressed Secretary of State John Kerry for assurances that the Syrian fighters would be properly vetted."
The House of Representatives approved President Obama's $500m request to help arm and train moderate rebels in Syria by 273 votes to 156. The proposal is expected to be adopted in the Senate.
The US carried out its first air strikes in Iraq in support of troops attacked by IS fighters on Tuesday.
Mr Obama's new strategy plans similar attacks in Syria and calls on a coalition of 40 countries to confront the militant group.