President Donald Trump again dismissed the Iran nuclear accord as awful for America, as he prepares to announce a key decision on whether to certify Iran's compliance with it.
Royce, like every other Republican in the U.S. Congress, opposed the nuclear agreement reached under President Barack Obama, a Democrat, in 2015 and signed by the United States, Iran, China, Russia, Britain, France, Germany and the European Union.
Engel said at the hearing that killing the deal would be a "grave mistake", since it is in place and backed by US allies and other powers.
If Congress does not act, however, it would leave the agreement in place.
Iranian officials have said they will not renegotiate.
Iran has already threatened the U.S. with dire consequences if it imposes sanctions against the country.
May's office said she and Trump spoke late Tuesday and both sides agreed their teams would remain in contact ahead of Trump's decision on the pact. In a recent review of Iran's compliance of the deal, the White House found the country to have met the requirements, yet Trump insisted on scrapping the deal, stating it was no longer in the US' security interests.
It gave Iran sanctions relief in exchange for curbs on its nuclear program in a bid to prevent it from developing nuclear weapons. "It is these security implications that we continue to encourage the U.S.to consider".
Johnson is expected to meet with Ali Akbar Salihu, president of Iranian Atomic energy institution in London today.
Speaking at an global conference on enhancing nuclear safety in Rome, Salehi said that Washington's recent "delusionary negative postures do not augur well" for keeping the deal intact.
Some top figures in Congress are already deeply skeptical of the Trump effort to kill the deal, with Rep. Ed Royce (R-CA) saying the United States should "enforce the hell out of it" instead. But Trump more recently has said he does not expect to certify Iran's compliance with the October deadline looming.
If Trump announces the decertification of the Iran nuclear deal, Congress will reportedly have 60 days to re-impose economic sanctions against Iran that were withdrawn following the 2015 agreement.