U.S. senators will introduce legislation to impose new sanctions on Iran as soon as this week, Senate aides said on Wednesday, despite the Obama administration's insistence that such a measure would violate terms of an interim agreement to curb Tehran's nuclear program.
Iran's foreign minister has also said a new sanctions law would kill the agreement. In the interim agreement, Tehran agreed to limit uranium enrichment in return for an easing of international sanctions.
Robert Menendez, the Democratic chairman of the Senate Foreign Relations Committee, and Republican Senator Mark Kirk are finishing legislation that would target Iran's remaining oil exports and foreign exchange and seek to limit President Barack Obama's ability to waive sanctions.
However, the measure would impose the new sanctions only if the interim deal has gone nowhere in six months or Iran violates terms of the agreement. Supporters said that would comply with the administration's request to allow negotiators to pursue a comprehensive diplomatic solution to the Iran nuclear crisis.
But the measure faces an uphill battle to become law.
Administration officials have been pushing Congress hard not to go ahead, including a classified briefing for the entire 100-member Senate on Wednesday by Secretary of State John Kerry and Treasury Secretary Jack Lew.
The session seemed to have done little to change lawmakers' minds.
Republican Senator Lindsey Graham, a supporter of the Menendez-Kirk plan, said after the meeting that the sanctions bill should go ahead.
"Giving the administration a six-month period to negotiate a successful deal makes sense to me. But having sanctions hanging over the head of the Iranians if the deal is not acceptable also makes sense to me," Graham told reporters after the meeting with Kerry and Lew.
Graham said he anticipated a vote on the plan in January. He insisted it would win enough support not only to pass, but also the two-thirds majority needed to override a veto.
But other senators expressed skepticism.
Democrat Dianne Feinstein said Kerry and Lew "made a very compelling presentation" and she was convinced Congress should hold off on any sanctions to allow negotiators to pursue a final agreement.
"The key is the comprehensive agreement," she told Reuters after the briefing.
Obama has said he can envision a final agreement that would ensure Iran does not have the capacity to build a nuclear bomb. Tehran says its nuclear program is entirely peaceful.