The move coincided with President Donald Trump's announcement of a broad strategy
to rein in Iran's nuclear ambitions, support of terrorism, human rights abuses, and growing influence over its neighbors that the US considers troublesome and destabilizing.
Legislation being drafted by Senate Foreign Relations Chairman Bob Corker, would "snap back" sanctions on Iran if it were to "violate enhanced and existing restrictions on its nuclear program," according to a summary of the bill. Corker told reporters that the plan was that the US would not leave the 2015 multi-lateral agreement, known as the Joint Comprehensive Plan of Action (JCPOA), although Trump later threatened he might.
If the agreement fell apart, Iran might quickly ramp up its nuclear program.
"Over the last several months, we have been working closely with the State Department, National Security Council and (Republican Sen. Tom Cotton of Arkansas) to develop a legislative strategy to address bipartisan concerns about the JCPOA without violating US commitments," said Corker, a Tennessee Republican.
The bill is aimed at addressing what the White House and other critics claim are flaws in the agreement, which was brokered with Iran by the Obama Administration, and five other countries -- Russia, China, Britain, France and Germany.
Those concerns deal with retiring key provisions after eight years and the full agreement after 15 years, problems with verifying that Iran is abiding by the accord and worries that, under the agreement, Iran can continue nuclear research and development.
"I am directing my administration to work closely with Congress and our allies to address the deal's many serious flaws," Trump said in his speech Friday.
"In the event we are not able to reach a solution with Congress and our allies, then the agreement will be terminated," the President added. "It is under continuous review and our participation can be canceled by me, as President, at any time."
Corker, who opposed the nuclear deal, said he would introduce a bill as early as next week and move it through the regular legislative process, including hearings in his committee, with a desire to complete action within 90 days. He stressed that he has already talked to Senate Minority Leader Chuck Schumer, D-New York, and Sen. Ben Cardin, D-Maryland, about building bipartisan consensus.
But House Minority Leader Nancy Pelosi, D-California, said she has not been briefed on the legislation.
"We haven't seen any of it on the Democratic side," she told reporters with frustration in her voice.
House GOP leaders haven't signaled if they will adopt a similar approach as Corker's legislation, but top Republicans on committees dealing with national security sent out a statement Friday announcing that, separate from the JCPOA, the House would vote on sanction measures targeting Iran's ballistic missile program and support for terrorist groups.
Corker also said he had lobbied European allies, who are reluctant to change the agreement, and hoped Trump would as well.
Cotton is a leading hawk on Iran and met privately with Trump at the White House last week.
"Lawmakers need to do now what we couldn't do two years ago: unite around an Iran strategy that truly stops Iran's nuclear weapons program and empowers the United States and our allies to combat the full spectrum of Iran's imperial aggression," said Cotton.
Trump's tough new approach to Iran won praise from congressional Republicans and was met with concern by Democrats, many who worry about killing the deal Obama worked so hard to put in place.
"The nuclear agreement struck by the previous administration with Iran is fatally flawed," said House Speaker Paul Ryan, R-Wisconsin. "I support President Trump's decision to reevaluate this dangerous deal, and the House will work with his administration to counter Iran's range of destabilizing activities."
"I look forward to working with my colleagues in Congress on additional legislation to increase sanctions and other pressure to hold Iran accountable for its broader destructive behavior in the region," said Sen. John McCain, R-Arizona, the chairman of the armed services committee. "I am also eager to collaborate with our partners and allies to revisit the most problematic provisions of the nuclear deal, and support a unified, forceful international front in the event that Iran materially breaches the terms of the agreement."
The top Democrat on the House foreign affairs committee, New York's Eliot Engel, said Iran must never be able to obtain a nuclear weapon but that Trump's approach is wrong.
"The President's plan doesn't make sense. Negotiating additional terms to the nuclear deal requires a coalition of international partners, not unilateral congressional action," said Engel. "And while we must crack down on Iran's other destabilizing actions -- ballistic-missile development, sponsorship of terrorism, human-rights abuses, and support for the Assad Regime -- Congress already passed tough sanctions against Iran, Russia, and North Korea last August, which the President grudgingly signed. But the Administration seems unwilling to enforce this new law."
"Not even one year into his Presidency, this is one of the most dangerous and consequential decisions the President has made imperiling US national security," said Cardin, the top Democrat on the Senate foreign relations committee. "It is now up to Congress to show the world that there is bipartisan support for the United States to uphold its commitments, including the JCPOA."
In a statement, Schumer, who opposed the original deal, predicted Congress would not scrap it.
"President Trump's own Secretary of Defense and Chairman of the Joint Chiefs of Staff, Generals Mattis and Dunford, both said that it's in our national security interest to keep the JCPOA in place and I agree," said Schumer. "I believe Congress, both Democrats and Republicans, will heed their recommendation."