President Obama says he will veto proposed bipartisan legislation to impose new sanctions on Iran so long as diplomatic negotiations over a nuclear deal remain underway.
"I will veto a bill that comes to my desk," Obama said in response to a question from ABC News at a joint news conference with visiting British PM David Cameron.
Obama said hitting Iran's economy with new sanctions in the next 60 to 90 days would violate an interim agreement reached last year, deepen recriminations, and heighten the risk of a military confrontation.
"There is no good argument for us to undercut, undermine the negotiations until they play out," Obama said.
"Congress needs to show patience," Obama said.
If a deal is not reached, with assurances that Iran could not obtain a nuclear weapon, "I would be the first one to come to Congress to say we need to tighten the screws," he added.