US President Barack Obama warned lawmakers on Friday not to trigger new sanctions against Iran over its nuclear program, vowing to veto any new sanctions legislation.
He also said such a move would upset diplomatic talks and increase the likelihood of a military conflict with Tehran.
In a joint news conference at the White House, Obama and British Prime Minister David Cameron urged members of the US Congress to be patient and hold off on legislation calling for further sanctions.
"There is no good argument for us to try to undercut, undermine the negotiations until they've played themselves out," Obama told reporters.
"Congress needs to show patience," he added. "My main message to Congress is: 'Just hold your fire.'"
Obama said he told Democratic lawmakers he would veto a bill calling for new sanctions if it landed on his desk.
The joint push with Cameron, who said he had personally called US senators about the issue, represented the strongest effort yet by the White House to prevent US lawmakers from both parties from seeking to force additional penalties on Tehran.
***50/50 Chance
The United States, Britain, France, Germany, Russia and China are in talks with Iran to forge a deal over Tehran's nuclear program. They failed to meet a self-imposed deadline for a solution in November. Obama put the chances of an eventual deal at 50/50.
The president warned that if the Congress forced further sanctions, Iran could use that as an excuse to abandon the talks and accuse Washington of blowing up the deal and acting in bad faith.
"There would be some sympathy to that view around the world, which means that the sanctions that we have in place now would potentially fray," Obama said.
"Congress should be aware that if this diplomatic solution fails, then the risks and likelihood that this ends up being, at some point, a military confrontation is heightened. And Congress will have to own that as well."
He clarified, however, that if a deal did not emerge, that did not mean Washington would shift toward a military posture.
***Not on War Footing
"I am not, repeat not, suggesting that we are on immediate war footing should negotiations with Iran fail," he noted. "The bottom line is this: We may not get there, but we have a chance to resolve the nuclear issue peacefully."
Republican and Democratic lawmakers are moving forward with a new sanctions bill, and some lawmakers reacted angrily to Obama's remarks.
"No White House threat will stop us from doing the right thing to protect the United States and its allies," House Speaker John Boehner said in a statement.
A Democratic co-sponsor of the bill to impose new sanctions on Iran if there is no agreement on its nuclear program by July said on Friday he stood by the legislation in the face of warnings that it could torpedo international negotiations.
"All I'm saying is let us put in prospective sanctions that don't get imposed ... until July," Senator Robert Menendez said when asked about Iran during an event in his home state of New Jersey.
Republican House of Representatives Majority Leader Kevin McCarthy said he was "offended" by Obama's remarks, saying they seemed to insinuate that lawmakers' concerns about Iran were driven by political considerations.
In a statement, McCarthy called on Obama to work with Congress to increase pressure on Iran.
Menendez, the top Democrat on the Senate Foreign Relations Committee and a longtime backer of tough sanctions on Iran, said he had a "fundamental disagreement" with the White House on the issue.
Claiming that Iran did not yet seem willing to make significant concessions after 18 months of negotiations, he suggested that new sanctions legislation might help convince them.
The bill Menendez is working on with Senator Mark Kirk, an Illinois Republican, would impose sanctions if there is no nuclear agreement by a June 30 deadline, but also includes a provision that would allow Obama to put them off for 30 days if an agreement were imminent.
Kirk also backed action in Congress.
"If anything can stop Iran from getting nuclear weapons, it is maintaining the united bipartisan front in Congress to end Iran's uranium enrichment and plutonium paths to the bomb," he said in a statement.
Iran denies its nuclear work has any military objective, saying the program is solely for peaceful applications, such as power generation.
