Secretary of State John Kerry downplayed hopes for a nuclear deal with Iran, as President Obama was to urge key senators to hold off deciding on new sanctions. Israeli Prime Minister Binyamin Netanyahu, meanwhile, said in an interview published Tuesday Iran had enough enriched uranium to make five nuclear bombs. The five permanent U.N. Security Council members -- the United States Britain, France, Russia and China -- plus Germany are to meet with Iran in a new round of talks in Geneva, Switzerland, starting Wednesday. The talks, billed as picking up where failed talks in Geneva left off 10 days earlier, are to pursue a first-step, six-month agreement in which Iran freezes its nuclear program in return for a letup of economic sanctions. The agreement would give negotiators "breathing room" to work out a comprehensive agreement that would end a 10-year impasse over Iran's disputed nuclear program, diplomats say. The United States, Israel and other allies maintain Iran is covertly trying to develop a capacity to build nuclear weapons, a charge Tehran denies, insisting its nuclear ambitions are limited to the peaceful generation of electricity and other civilian uses. "I have no specific expectations with respect to the negotiation in Geneva, except that we will negotiate in good faith and we will try to get a first-step agreement," Kerry said at a State Department news conference. At the same time, Obama was to meet at the White House with Senate leaders from both parties at 10:45 a.m. Tuesday in the hope of persuading the lawmakers to hold off on imposing crippling new sanctions against Iran, the White House said. Lawmakers and Israel argue more sanctions are needed to bring about a strong, accountable agreement with Tehran. Obama was to meet with the chairmen and ranking members of the Senate Banking, Foreign Relations, Armed Services and Intelligence committees, as well as with other committee members, the White House said. Adding new sanction layers on the Persian Gulf country would likely seriously complicate the Geneva talks, jeopardizing the chances of a deal, and strengthen hardliners in Tehran who want to see the collapse of Iranian President Hassan Rouhani's diplomatic initiative, diplomats say. Obama and other administration official stress only "reversible" sanctions would be eased -- ones that could be reimposed if Iran were to break any deal. At the State Department, Kerry said he hoped Iran would "understand the importance" of going to Geneva "prepared to create a document that can prove to the world that this is a peaceful program. That's always been our standard." "Now, I'm not going to negotiate this in public," Kerry said at the news conference with his Turkish counterpart, Foreign Minister Ahmet Davutoglu. "We all need to be respectful of each other's processes here and positions. And so I think it's best to leave that negotiation to the negotiating table." He said he did not plan to participate in the talks and declined to discuss details of a proposal under discussion. State Department spokeswoman Jen Psaki said Kerry would go to Geneva only if "it would be advantageous to the negotiations." She said the department expected to make a decision about this "later this week." French President Francois Hollande said in Israel Sunday he expected the so-called P5-plus-1 talks with Iran would lead to an agreement -- a prospect Netanyahu has said he vehemently opposes because it would "gravely" hurt Israel's security. Kerry told reporters Monday Netanyahu had "every right in the world to publicly state his position and defend what he perceives as his interests." But Kerry said the accord, if it is reached, would reduce Israel's security risk, not increase it. "I can assure those friends and everybody else watching this that nothing that we are doing here, in my judgment, will put Israel at any additional risk," Kerry said. "In fact, let me make this clear: We believe it reduces risk. We believe it helps all of us to move closer to this goal of achieving the comprehensive agreement." Netanyahu, escalating his lobbying effort against an interim deal, told German newspaper Bild Iran already possessed enough enriched uranium to make five nuclear bombs. "The Iranians already have five bombs' worth of low-enriched uranium," he said in an interview published Tuesday. "If you press the sanctions now, you might actually get a better deal," he said. "If you have a bad diplomatic solution -- what this appears to be -- you actually may get the consequences you want to avoid. That is, you would have no choice but to exercise a military option in the future." Russian President Vladimir Putin told Rouhani by phone Monday he saw a "real chance" for a nuclear deal, the Kremlin said.