UNITED NATIONS – As Secretary of State Rice urged the U.N. Security Council to take “strong steps” against Iran’s boasts this week of a nuclear breakthrough, advocates of a softer line called for caution yesterday, and some top council members attempted to downplay the mullahs’ defiance.

American ambassador to the United Nations, John Bolton, and his British counterpart, Emyr Jones Parry, said the council should increase the pressure on Iran and take action under chapter seven of the U.N. Charter, which allows for punitive measures in case of noncompliance with U.N. resolutions.

But American and European calls for sanctions against Iran met resistance from Russia and China, both of whom yesterday drew attention to the perils of reported plans for Western military action.

“If such plans exist, they will not be able to solve this problem,” Russian Foreign Minister Sergei Lavrov said, according to Russian news agencies. “On the contrary, they could create a dangerous, explosive blaze in the Middle East, where there are already enough blazes.”

Without Iran’s compliance, Mr. Bolton said that in the meantime, “We would consider a resolution under chapter seven” that makes a resolution binding and enforceable. Mr. Jones Parry added that “if there is no compliance,” the council should “make compulsory what is now an urging.”

Iran’s announcement on Tuesday that it successfully enriched uranium to 3.5% and yesterday’s boast that it intended to continue enrichment on an industrial scale defied the March 29 Security Council call on Iran to cease all enrichment activities. But China’s ambassador to the U.N., Wang Guangya, urged caution before moving to the next step against Iran.

“Certainly, I think what they did is not in line with what we requested,” Mr. Wang said. However, he stressed, the Iranians vowed their nuclear activity is for peaceful purposes, they have not withdrawn from the Nuclear Non-Proliferation Treaty, and they accepted international inspections of their nuclear facilities. “So there are two sides to this coin,” he said.

Mr. Wang said that next week high-level diplomats will meet in Russia to contemplate the next steps on Iran. “We are sending people to Moscow,” Mr. Wang told reporters, adding that the five permanent council members and Germany will meet at the level of foreign ministry Political Directors in Moscow on April 18. However, several top U.N. ambassadors were totally un aware of the Moscow meeting. “That’s news to me, I guess,” Mr. Bolton said when asked about it.

The political director at the State Department, Nicholas Burns, has been at odds with Mr. Bolton on several policy points.

In Washington, Ms. Rice said that the Security Council will “need to take into consideration this move by Iran and that it will be time for strong steps to maintain the credibility of the international community.” The world “does not believe that Iran should have the capability and the technology that could lead to a nuclear weapon,” she added.

In Iran, however, the nuclear organization’s deputy chief, Mohammad Saeedi, said Iran intended to speed up its enrichment program to involve 54,000 centrifuges. The technology of daisy-chaining centrifuges is considered the most delicate part of the enrichment process. “We will expand uranium enrichment to industrial scale at Natanz,” Mr. Saeedy told national television.

The barrage of announcements was meant “to strengthen Iran in its negotiations with the international community,” Israel’s army intelligence chief, Amos Yadlin, told several Israeli news outlets in special interviews published on the eve of Passover.

But he added that the Iranian boasts should not be taken at face value. “This is significant progress, but the fact that they can ride a bike does not mean that they will be able to ride at 80 kilometers [50 miles] per hour without falling off,” he said.

The Director of the International Atomic Energy Agency, Mohamed El-Baradei, was scheduled to arrive in Tehran last night in what originally was designed as a last-ditch effort to jumpstart stalled diplomacy. President Ahmadinejad’s announcement on Tuesday was seen as Iran’s answer to U.N. efforts.

Before demanding the toughening of diplomacy on the Mullahs, Ms. Rice called Mr. ElBaradei, who is scheduled to report to the Security Council on Iran’s compliance by April 28. Several diplomats yesterday said that before moving forward, the council would have to await his report, but Mr. Bolton said the council might move ahead earlier.

Secretary-General Annan also spoke with Mr. ElBaradei on the phone yesterday and afterward called on “everyone” to “cool down on the rhetoric, and not to escalate.” Mr. Annan said he hoped Mr. ElBaradei would be able “to convince the Iranian partners to come back to the table” and renew negotiations. He failed to mention that the Iranians have defied the Security Council’s demand to halt all enrichment activity.