Members of the US Congress from both parties introduced a bill on Thursday calling for denying Iran a nuclear bomb by any means necessary, days after US President Trump appeared to downplay a military option.

“An Iran that has nuclear weapons is unacceptable and a danger not only to our closest ally, Israel, but also to the whole world,” Representative Mike Lawler, a sponsor of the legislation, said in a statement.

“We must keep all options on the table when it comes to dealing with this unprecedented situation," the New York Republican added.

President Donald Trump on Tuesday reinstated the so-called maximum pressure policy on Iran from his first term but said he hoped not to implement the measures, saying he preferred a deal.

The next day, Trump said reports of US-Israeli collaboration on a devastating military attack on Iran were "greatly exaggerated".

Iran denies seeking nuclear weapons but US ally Israel says its Mideast mortal enemy is developing a bomb, which it views as an existential threat.

“If the Iranian Ayatollah and his henchman obtain a nuclear weapon, it would be one of the most destabilizing and dangerous events in world history," South Carolina Republican Senator Lindsey Graham said in the statement.

"This is not an authorization for the use of military force, but a resolution establishing the truth regarding Iran’s nuclear intentions and capability.”

The statement did not elaborate on the options cited and stops short of explicitly proposing military action.