Republicans on the House Homeland Security Committee this week urged President Biden to reconsider lifting sanctions on Iran, warning that doing so would be a "historic mistake" while saying that the nation poses an "ever-imminent threat to American democracy and national security."

The letter, signed by committee Ranking Member John Katko, R-N.Y., and Republicans on the panel, comes after the Biden administration ended the Trump administration’s position on the "snapback" of U.N. sanctions on Tehran.

REPUBLICANS SLAM BIDEN'S MOVE TO DROP IRAN SANCTIONS PUSH

"In the interest of homeland security, we write to express our gravest concern over the possibility of sanctions relief for the Islamic Republic of Iran," they wrote to the president. "As one of the longest standing countries listed by the U.S. State Department as a State Sponsor of Terrorism, Iran has repeatedly provided support for acts of international terrorism and has shown flagrant disregard for any restrictive measures placed upon the regime’s nuclear program."

Republicans pointed to Iran’s "malign activities," including its nuclear program, ballistic and cruise missile development, weapons proliferation, "support for terrorism, hostage-taking, cyberattacks, and gross human rights violations," calling them "unconscionable."

"Regime demands for sanctions relief as a prerequisite for the Administration’s proposed bilateral negotiations are not made in good faith," they wrote. "Rather, Iran will remain receptive only to measures which fit its own interests in seeking nuclear armament."

They added: "The United States must apply immense pressure to the Iranian regime and cannot afford to be perceived as weak or wavering on these important national security threats. Appeasement will not effectuate change."

The Republicans noted that it is the policy of the U.S. "not to allow Iran to develop or otherwise acquire a nuclear weapons capability," and said that sanctions are "an important point of leverage if we intend to achieve this goal diplomatically and peacefully."

"Lifting sanctions will only serve to back the United States into an inescapable corner and removes any power we hold in our attempts to normalize Iranian and United States relations," they wrote, adding that the "first duty in governing is to protect American national security."

"Any decision by the Biden administration to provide sanctions relief to Iran would be an historic mistake that placates a dangerous and erratic nation which poses an ever-imminent threat to American democracy and national security," they wrote. "Under no circumstance can we allow Iran to develop a nuclear weapon."

The Republicans added: "We implore you to reconsider lifting these sanctions."

POMPEO, OTHER CRITICS PAN BIDEN WH OFFER TO RESTART IRAN NUCLEAR TALKS

The letter came after Iran's supreme leader earlier this month urged the United States to lift all sanctions if it wants Iran to live up to commitments under its nuclear deal with world powers. 

"If (the U.S.) wants Iran to return to its commitments, it must lift all sanctions in practice, then we will do verification … then we will return to our commitments," state TV quoted Ayatollah Ali Khamenei as saying.

Former President Donald Trump unilaterally withdrew the U.S. in 2018 from the deal, which saw Iran agree to limit its enrichment of uranium in exchange for the lifting of economic sanctions. Biden has said he will seek to revive the deal but insisted that Iran must first reverse its nuclear steps, creating a contest of wills between the nations. 

In response to Trump's so-called "maximum pressure" campaign against Iran, the country began to gradually violate its atomic commitments and threatened further provocations in a bid to increase its leverage and get Biden to prioritize a return to the deal as he moves to dismantle Trump's legacy. Biden has signed a series of executive actions that reverse course on a wide range of issues, including climate change and immigration.

The Trump administration triggered the "snapback" mechanism in August, which would restore all U.N. sanctions that expired under the 2015 Iran nuclear deal. That move came after a failed effort by the U.S. to extend an arms embargo on Iran that was set to expire in October as part of the 2015 deal and barred the regime from buying and selling arms from allies.

However, that effort to snap back the sanctions was rejected by the U.N. Security Council, which said the U.S. had no authority to use the mechanism since it was part of the deal from which the U.S. had withdrawn. 

Then-Secretary of State Mike Pompeo dismissed the U.N. arguments, claiming it was part of the accompanying U.N. resolution of which the U.S. was still a participant.

But the Biden administration has sought to take a different approach to the Iranian regime and has sought to reenter the Iran deal. As part of that, the State Department said a letter had been sent to the council reversing the U.S. position on the snapback.

The Biden administration last week said Iran must return to complying with the nuclear agreement before the U.S. would reenter the deal. However, the State Department last week refused to rule out a step-by-step, sequenced approach to returning to the nuclear deal.

The move by the administration is one of a number of moves to reverse Trump-era foreign policy. Biden has reentered the U.S. in the Paris climate deal and has halted the withdrawal of the U.S. from the World Health Organization (WHO).

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In a speech to European leaders on Friday, Biden indicated he was trying to turn the page on the Trump era.

"I'm sending a clear message to the world, America is back, the transatlantic alliance is back and we’re not looking backward, we’re looking forward together," he said during a virtual address to the annual Munich Security Conference.

Fox News' Rich Edson, Adam Shaw and The Associated Press contributed to this report.