Obama Tells Lawmakers to Give Iran Sanctions More Time

President Obama, defending his diplomatic efforts in the face of congressional criticism, pleaded with lawmakers on Thursday to hold off on imposing new sanctions against Iran while negotiators seek a six-month interim agreement that would freeze Tehran’s nuclear program.

“Let’s test how willing they are to actually resolve this diplomatically and peacefully,” Mr. Obama said to reporters at the White House. “We will have lost nothing if at the end of the day it turns out that they are not prepared to provide the international community the hard proof and assurances necessary for us to know that they’re not pursuing a nuclear weapon.”

After negotiators from the United States and five other countries came close to a deal last weekend in Geneva, Mr. Obama said it did not make sense “to add new sanctions on top of the sanctions that are already very effective and that brought them to the table in the first place.”

Negotiators plan to meet again with Iran next week in Geneva. But the diplomatic near miss has provoked a storm of protest from Israel and criticism from Republicans and some Democrats, who say the White House plans to unravel the sanctions program in return for concessions that will barely slow Iran’s march to a nuclear weapon.

On Wednesday, Vice President Joseph R. Biden Jr. and Secretary of State John Kerry met with members of the Senate Banking, Housing and Urban Affairs Committee, which is considering a new set of sanctions that aim to drive Iran’s oil exports to zero. Mr. Biden and Mr. Kerry asked the senators to hold off on the bill to give diplomacy a chance. But there was little evidence that the senators were persuaded.

“I am dubious of the proportionality of the deal,” said Senator Charles E. Schumer of New York, the third-ranking Democrat in the Senate. “While I am exploring further details, I am worried that we are reducing sanctions while Iran is not reducing its nuclear capabilities.”

Mr. Obama disputed that, saying that under the interim deal being discussed, the United States would offer “very modest relief at the margins of the sanctions that we’ve set up.”

“Importantly, we would leave in place the core sanctions that are most effective and have the most impact on the Iranian economy — specifically oil sanctions and sanctions with respect to banks and financing,” the president said.

Mr. Obama said an interim deal would halt Iran’s program; dilute its stockpile of highly enriched uranium, which can be quickly converted to weapons-grade fuel; and subject Iran’s facilities to more vigorous inspections. That would give both sides the breathing space to conduct talks on a comprehensive deal.

If those talks fail, the president said, Congress can easily ramp up the sanctions again.