A vote granting authority for the US military to train and arm moderate Syrian rebels is an important step toward confronting the Islamic State (IS) group, President Barack Obama said.
The Republican-controlled House voted overwhelmingly to authorise the programme. A Senate vote is expected as early as today.
Mr O bama says the House vote shows there is bipartisan support for a critical component of his strategy to confront IS extremists, who have seized territory in Iraq and Syria.
The president says the training will not be conducted in Syria and US military personnel will not be on the ground in Syria as part of the programme.
He says the US has learned from fighting al Qaida that it is better to use America's capabilities to help partners on the ground defend themselves.
Meanwhile Iran's foreign minister ruled out co-operating with the US in helping Iraq fight IS militants, and warned the terrorist group poses a much broader global threat that needs new thinking to eradicate.
Mohammad Javad Zarif said Iran has serious doubts about the willingness and ability of the US to react seriously to the "menace" from IS "across the board" and not just pick and choose where to confront it as it has just started doing in Iraq.
"This is a very mobile organisation," he told the council on foreign relations in New York.
"This is not a threat against a single community nor a threat against a single region. It was not confined to Syria, nor will it be confined to Iraq. It is a global threat."
The US-Iranian relationship is at a delicate moment, with a new round of talks on a deal to rein in Iran's nuclear programme set to begin today, which Mr Zarif said is his top priority.
Leaders of the two countries - who talked a year ago - are also arriving next week for the annual ministerial meeting of the UN General Assembly.
Iran was the first country to provide help to neighbouring Iraq when the IS group swept across the border from Syria in July.
France wanted Iran to attend an international conference in Paris on Monday aimed at co-ordinating actions to crush the IS extremists in Iraq, but the US said "no".
Mr Zarif called the 24 participating nations at the Paris conference "a coalition of repenters" because most supported the IS group "in one form or another" from its inception following the US invasion of Iraq in 2003.
At the end of the day, he said, they created "a Frankenstein that came to haunt its creators".
Mr Zarif said Iran's assistance - without any troops - helped Iraq prevent IS from taking over Baghdad and the Kurdish capital Irbil.
He said the international community must begin to deal with the resentment and disenfranchisement that allows IS to attract young people from the Middle East, Europe and the US.
Mr Zarif agreed with Mr Obama that the group is neither Islamic nor a state so he referred to it by a previous name, ISIS. But he was critical of the US approach to dealing with the threat from the group.
In Iraq, where the US is carrying out airstrikes, he said, "it will not be eradicated through aerial bombardment".
When he was asked what circumstances could lead the two countries to collaborate or even discuss the threat posed by IS in Iraq, he said he told US secretary of state John Kerry that Iran has two fundamental principles - "it should be for the Iraqis to decide and we should not be rewarding terrorists".