(Reuters) - U.S. President Barack Obama dropped his opposition on Tuesday to a bill giving Congress a voice on a nuclear deal with Iran after members of his Democratic Party negotiated changes to the bill that had won strong support from both parties.
White House spokesman Josh Earnest said Obama, who had said he would veto the proposed bill because it could scuttle the emerging Iran deal, could accept compromises that drew bipartisan Senate support.
"What we have made clear to Democrats and Republicans in the Senate Foreign Relations Committee is that the president would be willing to sign the proposed compromise that is working its way through the committee," Earnest said.
The compromise bill passed the Senate Foreign Relations Committee unanimously and is expected to pass the full Senate.
It requires the Obama administration to send the text of a final agreement to Congress as soon as it is completed, and blocks Obama's ability to waive many U.S. sanctions on Iranwhile Congress reviews the deal.
It allows a final vote on whether to lift sanctions imposed by Congress in exchange for Irandismantling its nuclear capabilities.
"The proper role for Congress in this effort is the consideration of the sanctions that Congress put in place themselves," Earnest told reporters. "It would not be an up or down vote on the deal."
United Nations sanctions and those imposed by other countries could be lifted if an agreement is reached on restricting Iran's nuclear program by a June 30 target date.
Foreign Relations Committee Chairman Senator Bob Corker, who wrote the bill, said the White House had agreed to go along with it only after it was clear there was strong Democratic support. "That change occurred only when they saw how many senators were going to vote for this," Corker said.
The bill that passed cut to 30 days from 60 the time in which Congress can review any final nuclear agreement and eliminated the requirement that Obama certify that Iran is not supporting acts of terrorism against the United States.
Instead, it requires the administration to send Congress regular, detailed reports on a range of issues including Iran's support for terrorism, ballistic missiles and nuclear program.
Obama has invested enormous political capital throughout his presidency in securing an international agreement to ensure Iran does not develop a nuclear weapon, relying on tight sanctions that crippled Iran's economy and forced it to negotiate.
Earnest told reporters Obama had also insisted that there should be bipartisan agreement that this would be the only legislation governing Congress's oversight of the Iran deal.
Some Republicans, and a few hawkish Democrats, have pushed additional sanctions to put even more pressure on Iran but those bills were put on hold while the Corker bill moved forward.
Obama had warned that allowing Congress to vote directly on a final nuclear agreement would undermine Iran's faith in Washington's commitment to uphold a deal.
A framework deal with Tehran reached by Britain, China, France, Germany, Russia and the United States on April 2 is part of an effort to limit Iran's nuclear program in exchange for relief from economic sanctions.
Iran says its nuclear program is for peaceful purposes and not to develop weapons capability, as many in the West fear.
Russia on Monday introduced a new wrinkle into the convoluted international wrangling around the nuclear talks by lifting a self-imposed ban on delivering its S-300 missile defense system to Tehran.
The move did not formally violate international sanctions, and the State Department said the administration did not believe it would disrupt the unity at the talks, but Secretary of State John Kerry raised concerns with Moscow.
The full Senate is expected to vote on the bill shortly. Lawmakers will have the chance to offer additional amendments before that vote, but the White House said it would veto the bill if it were changed.
Obama's strongest Democratic supporters said they would fight any effort to make the bill more restrictive.
"If this bill is altered in ways that threaten this once-in- a-lifetime opportunity, to deal with a looming crisis, I will use every tool at my disposal to stop that from happening," said Senator Barbara Boxer.