US President Barack Obama forcefully rebuffed critics of the just concluded nuclear deal with Iran, even chiding one reporter who questioned his stance on American prisoners left in Iran that "you should know better."

Obama met reporters at the White House on Wednesday as Vice President Joe Biden and his national security team started lobbying the Republican-led Congress to green-light the nuclear accord, wrote Fox News.

The newly hammered nuclear deal with Iran faces strong bipartisan opposition in both Houses of Congress.

"I'm hearing a lot of talking points being repeated about 'this is a bad deal,'" Obama said, adding that he does not expect Republicans to back the agreement.

Claiming that the other option left on the table is war, Obama asked his critics: "What is your alternative?"

Obama said with the deal, "we cut off every single one of Iran's pathways to a nuclear [weapons] programme."

The agreement would lift economic sanctions on Iran in return for limitations on its nuclear programme. Iran has denied allegations that its civilian nuclear programme is a cover-up for the uranium enrichment programme.

He later expressed his irritation when CBS News reporter Major Garrett asked why he is "content" when the release of US citizens imprisoned in Iranian soil has not been secured even when their cases have been raised.

"The notion that I am content, as I celebrate, with American citizens languishing in Iranian jails—Major, that's nonsense, and you should know better," Obama said.

"I've met with the families of some of those folks, and nobody's content."

He later said that teams are already working "diligently" towards their release, but stated that including their freedom in the bargaining process could allow Iran to use the prisoners as leverage for compromises.

The president also admitted there will still be "problems with Iran's sponsorship of terrorism" as well as other issues, but said that opposing the nuclear agreement because it does not fix those issues "defies logic."

House Speaker John Boehner has opposed the nuclear deal, with spokesperson Cory Fritz saying "there's little reason for Americans to believe this nuclear deal will do anything to stop Iran's drive for a bomb, or stop its efforts to promote terror and violence throughout the Middle East."

Obama's fellow Democrats have also expressed their doubts on the deal, but the President maintained that without it there would be "no limits" on Iran's nuclear programme and Tehran "could move closer to a nuclear bomb."

"We're basically legitimising Iran's nuclear programme," said Democratic Sen. Bob Menendez. "At the end of the day, the challenge here is that 10 to 12 years from now, does Iran have a pathway towards a full industrial-sized nuclear programme and the possibility of breaking out to a weapon? And if so, all you've done is delayed the question of Iran's nuclear ambitions."

Former Vice President Dick Cheney, meanwhile, called Obama's claim that nuclear proliferation has been halted a "lie."

"The one thing that really disturbed me was when he said we have, quote, stopped the proliferation of nuclear weapons. That's a lie. That's just the fact of the matter is that the situation we've got when Iran ends up with a nuclear weapons, that is bound to lead others in the region to protect themselves, and in effect, to acquire their own capability," he said.

Former Alaska Gov. Sarah Palin called on the Congress to "stop the madness" and thumb down the nuclear deal, according to Breitbart.

"We must build up the foundation again; rebuild the wall protecting our – and Israel's – sovereignty. There are 554 days until we do that, by fundamentally restoring America. In the meantime, Congress, stop the madness. Do your job. Veto Obama's act of capitulation. Take the white flag of surrender out of this President's hand."