Amid Israeli denunciations of what Prime Minister Benjamin Netanyahu called a "bad deal," U.S. Secretary of State John F. Kerry argued that the agreement would improve Israel's security because extensive new inspections would give the United States and its allies far more information than before on Iran's activities.
The six-month preliminary deal would pause Iran's nuclear enrichment program and roll back some elements of it in return for the easing of some economic sanctions.
"None of this is based on trust. It's not a question of trust. It's a question of having the verification and the intrusive inspections," Kerry said on CNN, in one of several television appearances as he made the rounds of Sunday morning interview programs.
Critics should compare the plan with the available alternatives, not with a hypothetical ideal outcome, Kerry added.
"This negotiation is not the art of fantasy or the art of the ideal. It's the art of the possible," Kerry said in an interview with ABC's George Stephanopoulos. "If you didn't do what we're doing, they would be marching forward" with the nuclear program and "moving closer to a weapon."
President Obama and Kerry hope to dissuade Congress from imposing any new sanctions on Iran while the next round of negotiations proceeds. New sanctions could cause the Iranians to withdraw from talks, officials have warned.
Despite strong attacks on the deal from the Israelis and some conservative groups in the U.S., initial reaction from Capitol Hill indicated that the administration may achieve that goal, at least for now.
The administration expects opposition from many Republicans and can count on the support of most Democrats. One key group being lobbied by both sides is Jewish Democrats and those with large numbers of Jewish constituents, who may be torn between a desire to back Obama and long-standing support for Israel.
White House officials held a 45-minute conference call with a group of Jewish members of Congress on Sunday, stressing the potential benefits of the deal.
"It's tough for all of us who are strongly pro-Israel to be at odds with the views of our Israeli allies," said Rep. Adam B. Schiff (D-Burbank), one of those who took part in the call. He suggested Congress would approve sanctions that would take effect if negotiations for a permanent deal fail.
"Even among the best of allies, you're going to have differences," Schiff added. "This deal has to be compared to the alternative" of Iran's being able to pursue its nuclear program without restraint.
"I hope that Congress will work with the administration to strengthen our hand during the course of the next six months and work in unison and not at odds with each other," he said.
Senate Foreign Relations Committee Chairman Robert Menendez (D-N.J.) issued a statement also suggesting that Congress would pass additional sanctions on a standby basis.
Menendez criticized the deal, saying it would give Iran too much relief from sanctions in exchange for relatively little rollback of its nuclear program. But he did not suggest any immediate action that might undermine the agreement.
"I expect that the forthcoming sanctions legislation to be considered by the Senate will provide for a six-month window to reach a final agreement before imposing new sanctions on Iran, but will at the same time be immediately available should the talks falter or Iran fail to implement or breach the interim agreement," he said.
Among Republicans, some, including Rep. Tom Cotton (R-Ark)., who is running for the Senate, compared the deal to then-British Prime Minister Neville Chamberlain's appeasement of Adolf Hitler in Munich, Germany, in the run-up to World War II.
House Foreign Affairs Committee Chairman Ed Royce (R-Fullerton) called for toughening sanctions. "We just feel more pressure needs to be brought on Iran rather than make this deal and take the pressure off of Iran," Royce said in an interview on Fox News.
House Speaker John A. Boehner, however, issued a notably mild statement that expressed doubts about the deal but did not propose any immediate steps that might try to undo it.
"The interim deal has been and will continue to be met with healthy skepticism and hard questions," Boehner (R-Ohio) said. "Iran has a history of obfuscation that demands verification of its activities and places the burden on the regime to prove it is upholding its obligations in good faith while a final deal is pursued."
Boehner stressed the need to "preserve the strong international sanctions regime" until a final deal can be negotiated. But his statement said nothing about imposing new sanctions on Iran immediately.
And some Democrats offered more full-throated praise.
Sens. Dianne Feinstein (D-Calif.), who heads the Senate Intelligence Committee, and Carl Levin (D-Mich.), the chairman of the Senate Armed Services committee, both of whom have long records of supporting Israel, lauded the deal.
Levin called it "a realistic, practical way to freeze Iran's nuclear program for six months while we seek a long-range diplomatic end to Iran's nuclear weapon ambition."
Feinstein called the agreement "a giant step forward" and said it "should not be undermined by additional sanctions at this time."
Sen. Bill Nelson (D-Fla.) said simply: "It is a choice between a pause or imminent war. I choose a verifiable pause."
Opponents of the deal moved quickly to try to stymie it.
"I don't see any likelihood that this is going to sell well in Congress," Danielle Pletka, vice president for foreign and defense policy studies at the American Enterprise Institute, said in a call Sunday with reporters.
"Once you start to lift sanctions, even minimally, it is a breach, a hole in the dike, and everything goes flowing back in," Pletka said. "That is absolutely what the Iranians are calculating."
Administration officials say that sanctions could be ratcheted back up if Iran fails to negotiate a final agreement, she said, but "we are already seeing Asian businessmen, Chinese in particular, headed toward Tehran to make deals. So every picture you see of the Iranians smiling, that's the reason."
Still, Pletka said she saw "very, very significant hurdles to getting Iran legislation passed with substantial enough majorities to withstand a presidential veto."
Rep. Brad Sherman (D-Sherman Oaks), a senior member of the House Foreign Affairs Committee, also said he thought the deal fell short. "Nine thousand centrifuges continue to spin," he said in an interview.
But he, too, said "the president will be able to block" any immediate move toward toughening the sanctions. The best move for those concerned about the deal would be to support additional sanctions that would go into effect if the administration fails to produce a final agreement satisfactory to Congress, he said.
"Our position in these negotiations will be much stronger if the Iranians know they have got to agree to something so that Congress passes a resolution delaying or eliminating the application of massive additional sanctions," he said.