UNITED NATIONS — European diplomats are expressing concern that Russia’s refusal to impose a new round of sanctions on Iran could spell an end to diplomacy and lead to a military attack to stop Tehran from developing nuclear weapons.

A Russian veto at the U.N. Security Council would scuttle any resolution on sanctions, which America is seeking over Iran’s refusal to dismantle its nuclear program. Relations between Washington and Moscow have turned icy since Russia’s war with Georgia this summer, though Russian diplomats are denying any “spillover” effect from the war into issues relating to Iran and North Korea, both of which have defied Security Council demands that they shut down their nuclear programs.

Still, the Russian foreign minister, Sergei Lavrov, who addressed the Council on Foreign Relations last night shortly after meeting with Secretary of State Rice for the first time since the war last month over the breakaway Georgian regions of South Ossetia and Abkhazia, said yesterday that America should clarify how much cooperation it wants from Russia.

Ms. Rice and her French counterpart, Bernard Kouchner, say that if Russia believes the time is not right for a new Security Council resolution on Iran, then the time is not right. But privately, Western European diplomats are expressing frustration that Russia is blocking any punitive measures on Iran, even after the International Atomic Energy Agency last week voiced its frustration with Tehran’s intransigence.

“If the Russians want an Israeli bombing, then go ahead,” a European diplomat who spoke on the condition of anonymity said.

“The General Assembly and the Security Council bear the responsibility for preventing agonies before they take place,” President Peres of Israel told the assembly yesterday, in a speech in which he denounced President Ahmadinejad’s anti-Semitic remarks on the same stage a day earlier. But Mr. Peres added: “Israel has shown that democracies can defend themselves. We do not intend to change.”

Israel has long maintained that while it prefers a diplomatic solution to resolve the standoff over Iran’s nuclear program, it will act militarily to stop the country’s ruling mullahs from obtaining an atomic bomb if diplomacy fails. The IAEA last week issued a report expressing frustration with Iran’s failure to cooperate with the agency’s nuclear inspectors, its director, Mohamed ElBaradei, said.

Mr. Lavrov insisted yesterday, however, that the IAEA report was more nuanced. “ElBaradei said other things in his report, but it’s only the frustration part which was quoted here,” he said.

On Tuesday, Russia abruptly announced that Mr. Lavrov would not join his fellow foreign ministers from the five permanent members of the Security Council and Germany, who were scheduled to meet to discuss a new round of sanctions, saying the time was not right for sanctions.

If the steering group on Iran, known as the P5 plus 1, wants to remain united, Mr. Lavrov said yesterday, the Security Council can easily pass a resolution saying: “We reiterate all the existing resolutions of the Security Council and we strongly call on Iran to implement all these resolutions.”

Such a resolution would “send a very clear signal,” Mr. Lavrov said.

America and its European allies have called on the council to impose a fourth round of sanctions on Iran during the General Assembly session this week. “The Russians said that they didn’t think the time was right,” Ms. Rice told CNBC. “We called them and said, ‘You’re absolutely right, let’s do it when we’re ready.'”

After a round of lower-level negotiations, the foreign ministers of the P5 plus 1 “are ready, all of us, to travel around the world and meet somewhere else, I don’t know where, in Paris perhaps,” Mr. Kouchner added. “We have to go on, and we will go on. Not only sanctions inside — another, let’s say, resolutions of the Security Council, as we did three times — but also national sanctions.”

Mr. Kouchner said the IAEA report meant there was “danger out of Iran.”

Last week, an Israeli intelligence official, Yossi Beidatz, reportedly told the Cabinet that Iran has already obtained between one-third and one-half of the fissile material it needs to build a bomb. The Russian foreign minister, however, said in a statement last week that Europe and America were overstating the nuclear danger posed by Iran.

Mr. Lavrov said that in his meeting with Ms. Rice yesterday, “I did not feel any rocky” relations with America, and he added that there were important items on the international agenda that call for cooperation. But he expressed anguish over Western statements on the war between Russia and Georgia, which he said failed to recognize Russia’s “responsibility to protect” the two separatist regions. Such statements made cooperation more difficult, he added.

“We have to understand if the United States has some sort of list of items in which she does not want to cooperate with us, and another list in which she does want to cooperate with us,” Mr. Lavrov said. “If we have such a list, we would certainly understand better how we ourselves should proceed in this relationship.”