UNITED NATIONS — Secretary of State Rice is signaling she won’t stand in the way of an Israeli military action to stop Iran’s nuclear program, ratcheting up the American pressure on Tehran.

Following the Iranian government’s latest refusal to give what Washington considered a “satisfactory” answer to the most generous offer yet that leading world powers have made to Tehran, the Bush administration vowed to impose a new round of Security Council sanctions. Council members say, however, that several weeks will pass before the divided body can impose punitive measures on Iran, if at all. Some diplomats even argue that any significant policy agreement among the powers on Iran must wait until next year, when a new American president takes charge.

Israel, a country Iran has threatened with annihilation, may not wait that long. Israel’s air force carried out a major drill yesterday, simulating a response to a coordinated missile attack against it by Iran, Syria, and Hezbollah, according to press reports. Israel also added new fighter jets and submarines to its arsenal recently. If the Iranians “provoke us, or attack us, our army is prepared to attack and to succeed uncompromisingly,” Defense Minister Ehud Barak told the Italian newspaper Corriere della Sera.

“We don’t say yes or no to Israeli military operations; Israel is a sovereign country,” Ms. Rice said in an interview with Yahoo and Politico, according to a transcript on the State Department’s Web site. She added, however, that Washington’s diplomacy on Iran is well-coordinated with Israel. “They’ve said that diplomacy can work here,” she said, referring to Jerusalem officials.

“Every day that the centrifuges continue to spin brings Iran closer to a nuclear weapons capability and threatens the stability and security of the region and the world,” Israel’s ambassador in Washington, Sallai Meridor, said. “The international community should immediately apply additional robust sanctions.”

In her interview, Ms. Rice dismissed as “not adequate” the Iranian response to an offer presented last month to Tehran by the European envoy Javier Solana in the name of the five permanent members of the Security Council and Germany. “We’ve always said Iran has a way out if they ever wish, but we will seriously pursue sanctions if they don’t,” she said.

The Security Council, which has imposed three rounds of mild sanctions on Iran since 2006, has traditionally taken its time before agreeing on compromise action that manages to satisfy Russia, China, and several European countries that prefer conducting business with Iran to halting its nuclear run. The process is also very slow, the American U.N. ambassador, Zalmay Khalilzad, acknowledged yesterday.

“As you know from the previous experience dealing with this issue, a lot of the negotiations about the sanctions, specifically what would be included, is negotiated outside the U.N. system,” Mr. Khalilzad said yesterday. Sanctions are discussed among foreign ministries before even reaching the United Nations, he added, and right now the talks are in the “capital-to-capital” stage.

“Since I haven’t heard anything here, in this building, to this point, I think it’s not entirely reckless to assume that September is the next opportunity,” the Russian ambassador at the United Nations, Vitaly Churkin, said, adding that “some progress has been made” in Mr. Solana’s negotiations with Iran. “Diplomacy is about patience,” he said, countering Washington’s contention that the six powers have agreed to impose sanctions. “Rather than focus almost entirely on sanctions, let’s focus on opportunities,” he said.

Other diplomats suggested an even lengthier time line for dealing with Iran than the start of the annual General Assembly debate, when world leaders arrive here in the last week of September. “Everyone is waiting for the next administration in Washington,” said a council diplomat who spoke on condition of anonymity, expressing an opinion shared by many officials here.

The International Atomic Energy Agency’s deputy chief, Olli Heinonen, arrived in Tehran yesterday to negotiate a process for clarifying remaining questions that the agency has on whether Iran’s nuclear program is designed, as it contends, purely for civilian purposes, according to press reports from Vienna and Tehran.

“Their goal is to obtain a nuclear weapon, and believing otherwise is an illusion,” Mr. Barak told the Italian newspaper yesterday. The time has come to act “with sanctions rather than with talk,” he said, adding that sanctions “must include Russia, China, and India.” For now, he said, “there is still time, because the sanctions are efficient. But I say this once again, firmly: The world and Israel must leave all options open. The disaster will be an Iran with nuclear weapons.”