The US House of Representatives has approved President Barack Obama’s plan to train and arm the moderate Syrian opposition taking on Islamic State.
The vote passed by a large majority in the Republican-controlled House and is expected to be adopted in the Senate.
The endorsement came after President Obama repeated that he would not be committing American combat troops to ground operations in Iraq.
The US has undertaken 174 air strikes against IS in Iraq since mid-August.
The jihadist group controls large areas of Syria and northern Iraq.
In the most recent air strikes on Tuesday and Wednesday, US forces destroyed two IS armed vehicles north-west of Irbil and several units south-west of Baghdad, according to US Central Command (Centcom).
Mr Obama’s new strategy plans similar attacks in Syria and calls on a coalition of 40 countries to confront the militant group.
Analysis: Tom Esslemont, BBC News, Washington
This 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. 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.
Some lawmakers from both parties feel sceptical that the Syrian rebels are 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 so that, in future, American weapons don’t fall into the wrong hands.
‘No safe haven’
On Wednesday, the House of Representatives approved his $500m request by 273 votes to 156 to help arm and train moderate rebels in Syria.
The provision has been added to spending legislation aimed at extending federal government operations beyond the end of September.
Earlier, Mr Obama said he would not commit “to fighting another ground war in Iraq”, while visiting a military base in Florida.
Mr Obama arrived overnight in Tampa, Florida, where Centcom – responsible for the Middle East and Central Asia – is based.
After briefings with top military officials, Mr Obama told an assembly of troops that “the American forces that have been deployed to Iraq do not and will not have a combat mission”.
But the US would see that IS was eventually defeated, Mr Obama said – “If you threaten America, you will find no safe haven.”
“We cannot do for the Iraqis what they must do for themselves,” Mr Obama said.
Mr Obama highlighted partner countries like France and the UK, which were already flying reconnaissance flights, and Saudi Arabia, which has agreed to host a US-led training programme for Syrian rebel groups fighting IS.
His comments came a day after Chairman of the Joint Chiefs of Staff Gen Martin Dempsey said he would recommend ground troops if the air strikes failed.
Iranian Foreign Minister Mohammed Javad Zarif said on Wednesday that Islamic State was a “dangerous phenomenon,” but could not be defeated by air strikes.
Meanwhile, Iraqi Prime Minister Haider al-Abadi rejected as “out of the question” the possibility that foreign ground troops would be allowed to fight in his country.
“Not only is it not necessary,” he told Associated Press, “we don’t want them. We won’t allow them. Full stop.”
IS earlier released what analysts described as a video response to the US moves.
The slickly produced, Hollywood-style trailer for a film entitled Flames of War refers to Mr Obama’s insistence that US combat troops will not be returning to fight in Iraq.
In an apparent taunt, it depicts wounded US troops, masked executioners standing over kneeling captives, and declares at the conclusion: “Fighting has just begun.”