A bill calling for Congress to have a say on an emerging nuclear agreement with Iran has turned into a tug of war on Capitol Hill, with Republicans trying to raise the bar so high that a final deal might be impossible and Democrats aiming to give the White House more room to negotiate with Tehran.

Senators of both parties are considering more than 50 amendments to a bill introduced by Sens. Bob Corker, R-Tenn., and Bob Menendez, D-N.J. The bill would restrict Obama's ability to ease sanctions against Iran without congressional approval.

The Senate Foreign Relations Committee on Tuesday is to debate the amendments and vote on the bill, which has pitted the White House against the GOP-led Congress on a critical foreign policy issue that President Barack Obama wants etched in his legacy. Obama administration officials, who are expected to continue lobbying lawmakers next week, don't want Congress to take any action before a final deal could be reached by the end of June.

There is strong support, however, from lawmakers of both parties who think they should be able to weigh in on any agreement aimed at preventing Iran from being able to develop nuclear weapons. Iran says its program is for civilian purposes, but the U.S. and its partners negotiating with Tehran suspect Iran is keen to become a nuclear-armed powerhouse in the Middle East, where it already holds much sway.

There have been intense negotiations on Capitol Hill for the past several days about ways to amend the bill. Advocacy groups and congressional staffers provided details about amendments, which still might be withdrawn or rewritten.

Under the bill as it is currently written, Obama could unilaterally lift or ease any sanctions that were imposed on Iran through presidential action. But the bill would prohibit him for 60 days from suspending, waiving or otherwise easing any sanctions Congress levied on Iran. During that 60-day period, Congress could hold hearings and approve, disapprove or take no action on any final nuclear agreement with Iran.

If Congress passed a joint resolution approving a final deal — or took no action — Obama could move ahead to ease sanctions levied by Congress. But if Congress passed a joint resolution disapproving it, Obama would be blocked from providing Iran with any relief from congressional sanctions.

In an effort to give the president more negotiating room, Maryland Sen. Ben Cardin, the new ranking Democrat on the foreign relations committee, and a few of his Democratic colleagues have proposed letting Obama waive congressionally imposed sanctions if not doing so would cause the U.S. to be in violation of a final agreement.

Several Democratic senators also have proposed shortening the congressional review period to 30 days or even 10 days that Congress is in session. Democrats also want to strike a part of the bill that requires the Obama administration to certify that Iran has not directly supported or carried out an act of terrorism against the United States or an American anywhere in the world.

On the Republican side, Sen. Marco Rubio of Florida, a likely presidential candidate, has proposed an amendment that would require the Obama administration to certify that Iran's leaders have publicly accepted Israel's right to exist. That's a tall order. Iran has threatened to destroy Israel and Israeli Prime Minister Benjamin Netanyahu has warned the U.S. about making a deal with Iranian leaders, whom he distrusts.

Dylan Williams, a lobbyist for the liberal Jewish group J Street, argues that Rubio's proposed amendment puts Republicans in a "lose-lose" position. Adopting the amendment would kill the Corker bill, Williams said, because many senators would vote against a provision they know the Iranians would never accept. Defeating the amendment, he said, would be seen as a slap at Netanyahu, whom GOP leaders have strongly supported on the Iran nuclear matter.

Republican senators also are contemplating amendments that would require that any final agreement be a treaty. That's also a high hurdle because treaties must be approved by two-thirds of the Senate.

Before any sanctions are eased, one of four amendments drafted by Republican Sen. John Barrasso of Wyoming would require the president to certify that any funds Iran received as a result of sanction relief would not facilitate Iran's ability to support terrorists or build nuclear weapons or ballistic missiles. He says he will formally introduce the amendments only if Democrats try to weaken the bill, which he supports.

And Sen. Johnny Isakson, R-Ga., has filed amendments to the bill to require Congress to address the issue of compensation for 52 Americans held hostage in Iran from November 1979 to January 1981 before any deal is finalized, any sanctions are eased or diplomatic relations with Iran are normalized.

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Associated Press writer Chuck Babington in Washington contributed to this report.