MOSCOW — Denting President Obama’s hopes for a powerful ally in his campaign to press Iran on its nuclear program, Russia’s foreign minister said Tuesday that threatening Tehran now with harsh new sanctions would be “counterproductive.”

The minister, Sergey V. Lavrov, said after meeting with Secretary of State Hillary Rodham Clinton here that diplomacy should be given a chance to work, particularly after a meeting in Geneva this month in which the Iranian government said it would allow United Nations inspectors to visit its clandestine nuclear enrichment site near the holy city of Qum.

“At the current stage, all forces should be thrown at supporting the negotiating process,” he said. “Threats, sanctions and threats of pressure in the current situation, we are convinced, would be counterproductive.”

Mr. Lavrov’s resistance was striking given that, just three weeks before, President Dmitri A. Medvedev said that “in some cases, sanctions are inevitable.” American officials had hailed that statement as a sign that Russia was finally coming around to the Obama administration’s view that Iran is best handled with diplomacy backed by a credible threat of sanctions.

It also came after the Obama administration announced that it would retool a European missile defense system fiercely opposed by Russia. That move was thought to have paid dividends for the White House when Mr. Medvedev appeared to throw his support behind Mr. Obama on Iran, though American officials say the Russian president was also likely to have been reacting to the disclosure of the secret nuclear site near Qum.

After the meeting with Mr. Lavrov, Mrs. Clinton met Mr. Medvedev later on Tuesday, and two administration officials said he did not retreat from his support in his private discussions with her. But he said nothing about Iran publicly before or after the meeting. Prime Minister Vladimir V. Putin, who has been skeptical of sanctions, was in China on a trade mission.

Mr. Lavrov said that the talks in Geneva between Iran and other countries had raised hopes for a diplomatic solution, and that it made no sense to discuss sanctions as long as those negotiations were under way. “We are maybe not 100 percent, but still have chances to succeed,” he said.

His position conflicts with that of the Obama administration, which argues that the threat of sanctions is crucial to the prospect for a diplomatic solution. Unless Russia and China join the United States and Europe in signaling that the sanctions may be necessary if diplomacy fails, American officials have said, Iran has less incentive to make concessions.

A Russian refusal to back sanctions could expose the Obama administration to criticism at home, where Republicans have argued that the president yielded to Kremlin concerns on the missile shield without getting much in return.

Enlisting Russia is critical for any sanctions campaign because of its geopolitical links to Iran. Russia’s refusal to act now may influence China, which has invested heavily in Iranian oil and gas reserves and has also been wary of sanctions. That Mr. Putin was in Beijing cutting deals while Mrs. Clinton was in Moscow warning about Iran was not lost on analysts here.

Though Mrs. Clinton also stressed the importance of diplomacy, she reiterated the administration’s view that there must be a parallel track of sanctions to prevent Iran from dragging its feet in negotiations.

“In the absence of any significant progress, we will be seeking to rally international opinion behind additional sanctions,” she said at the joint news conference with Mr. Lavrov.

Mrs. Clinton insisted the United States did not make any specific requests of Russia at the meeting. But a day earlier, a senior official traveling with her said that the United States would be looking for “specific forms of pressure” that Russia would be prepared to back.

The next major step in the diplomatic process will be on Monday, when Iran and officials from France and Russia are to meet in Vienna to discuss the details of a plan to ship a majority of Iran’s stockpile of lightly enriched uranium out of the country to be enriched in Russia to a higher grade. The uranium would then be returned to Iran, where it would fuel a research reactor.

That agreement was the most tangible result of the talks in Geneva between Iran and a group of countries: the United States, Britain, France, Germany, Russia and China. A senior American official said that in his meeting with Mrs. Clinton, Mr. Lavrov had told her that Russia was determined to hold Iran to the deal and would consider sanctions if the Iranians reneged on it.

While Iran dominated attention during Mrs. Clinton’s visit, her first trip to Russia as secretary of state, she and Mr. Lavrov discussed a wide range of issues, including the decision to redesign the missile-defense system.

Despite a clear warming trend since Mr. Obama took office, old strains remain, especially over the West’s role in the other former Soviet republics. In their meetings, officials said, Mr. Medvedev and Mr. Lavrov pointed to recent comments by a senior American defense official that the United States might consider including Ukraine in any future antimissile system.

Russia’s ties with Ukraine have grown contentious in recent years, as Ukraine has tilted toward the West. The comments by the American defense official, Alexander Vershbow, clearly irritated the Kremlin.

A senior American official said that the United States had no plan to install missile-defense equipment in Ukraine, but that it might use data from radar stations in the country.

Analysts here expressed little surprise at Mr. Lavrov’s refusal to threaten Iran. Fyodor Lukyanov, editor in chief of the journal Russia in Global Affairs, said the administration was misguided if it believed that there had been a fundamental shift in Russia’s position in recent weeks.

Mr. Medvedev’s comments during his visit to the United States last month represented more of a political gesture because of the missile-defense decision, rather than a Russian concession, he said.

“It was not based on a new assessment of an Iranian threat,” he said. “It was just a feeling that Russia had to be polite and react to what Obama did.”

Mr. Lukyanov pointed out that the United States and Russia approach Iran from sharply different perspectives. Russia and Iran are neighbors, and the Kremlin has for many years had positive dealings with Iran on regional issues, including unrest in Chechnya and in Central Asia.

“Iran is seen by Russia as much more rational and reliable than it is seen by the United States or Israel,” he said.

www.nytimes.com/2009/10/14/world/europe/14diplo.html