Republican leaders called on US President Barack Obama to retract a statement he made last week where he compared Republican lawmakers opposed to the Iran nuclear deal to Iranian hard-liners who habitually chant "Death to America."

In a statement released on Wednesday, Senate Majority Leader Mitch McConnell also called on Obama to approach the discussion on allowing Iran to continue its nuclear programme with the "reverence and respect it clearly deserves."

"The President needs to retract his bizarre and preposterous comments, and both supporters and defenders of the President's deal with Iran should reject this offensive rhetoric," McConnell said.

The Republican senator from Kentucky said Obama's remark was so blistering it must have offended even Obama's Democratic allies who are now opposed to the deal made with Iran.

Last Tuesday, New York Democratic Representatives Steve Israel and Nita Lowey as well as Florida Democratic Rep. Ted Deutch announced that they will join their Republican colleagues in rejecting the deal.

"I imagine the Democrats who've already come out against this agreement will be especially insulted by it... This goes way over the line of civil discourse," McConnell said.

"Let me repeat my call for the President to shelve these talking points no one believes and resist these insults no one deserves so we can all aim higher —and rise to the moment together," he said.

McConnell issued the statement in response to the speech Obama made at the American University in Washington where he staunchly defended the deal and blasted its critics ahead of the congressional review on the controversial pact.

Last July 14, the US joined five other world powers in agreeing to lift economic sanctions on Iran after the latter agreed to curb its nuclear activities. Under the deal, Iran will maintain but limit its ability to enrich uranium for peaceful purposes, keeping about a third of its 19,000 centrifuges capable of separating the explosive uranium-235 isotope from uranium ore.

The US Congress has about 60 days to review the deal which lawmakers can approve or disapprove following a vote or do nothing over.

Backed by Israel, opponents of the deal vowed to derail it by garnering the needed number of votes to override the expected presidential veto.

Obama warned that the United States will lose its credibility as "a leader of democracy" and as "an anchor of the international system" if Congress decides to kill the deal he negotiated together with other Western powers.