VIENNA, Austria — Talks meant to give Tehran a last chance to avoid U.N. sanctions over its nuclear defiance were postponed yesterday, with a senior Iranian envoy saying “a procedural matter” had caused a delay of several days.

“We will not have the meeting today in Vienna,” the chief Iranian envoy to the International Atomic Energy Agency, Ali Ashgar Soltanieh, told the Associated Press. “Both sides are arranging for a couple of days later.”

The talks had been tentatively set for yesterday in Vienna as a final attempt to see if enough common ground existed to start negotiations between Iran and the six nations that have been trying to persuade Iran to curtail its nuclear program.

But while the European Union’s Javier Solana had been ready to fly to the Austrian capital at short notice, the talks had been left hanging by uncertainty over whether the Iranian nuclear envoy, Ali Larijani, would come.

No immediate comment was available from Mr. Solana’s office in Brussels. Although Mr. Soltanieh said the decision to postpone any meeting had been mutual, it appeared that Iranian reluctance to attend had scuttled the chance of yesterday’s talks.

Mr. Soltanieh said “a procedural matter” had led to the postponement, but offered no details. In Tehran, Foreign Minister Manoucher Mottaki said only the time and place of any meeting was still “under discussion by both sides.”

Iran defied an August 31 deadline by the U.N.Security Council to freeze uranium enrichment. Still, the five permanent council members and Germany — the six powers attempting to entice Iran into negotiating on its nuclear program — had decided to hold off work on imposing sanctions until the outcome of any talks between Messrs. Solana and Larijani.

Senior negotiators of those six countries were to meet in Berlin on today to plan their further Iran strategy.

Iran’s unyielding stance appears to be based on the calculation that sanctions will be opposed by Russia and China, both veto-wielding Security Council members that have major commercial ties with Iran. America and key European allies Britain and France had agreed to wait for the result of talks between Messrs. Solana and Larijani in an attempt to mollify both Moscow and Beijing. In Moscow on Tuesday, a top Kremlin aide said Russia remained reluctant to impose sanctions on Iran, although this did not imply support for a nuclear-armed Iran.

“We could suffer more than anyone else if they built nuclear weapons,”a senior aide to President Putin, Igor Shuvalov, said.

But he cautioned that economic sanctions could further increase global oil prices and have a negative impact on regional stability. He added that Russia’s location next to Iran and former Soviet Muslim republics in Central Asia made it especially vulnerable.

“We don’t mind using a stick, but we don’t want that stick to hit us or our partners over the head,” he said.

China’s premier Wen Jiabao echoed Mr. Shuvalov’s sentiments, saying the six powers had to be cautious about moving toward sanctions because they may prove counterproductive.

But American officials on both sides of the Atlantic suggested the time had already come for punitive Security Council action. A State Department spokesman, Sean McCormack, said in Washington that the Security Council had made clear in a resolution that it was prepared to vote for sanctions if Iran failed to meet the August 31 deadline to suspend enrichment.

Mr. McCormack said Tuesday that America intended to proceed “down that pathway.”

Echoing those comments, Gregory Schulte, chief American delegate to the International Atomic Energy Agency, accused Iran’s leaders of making “a strategic decision to acquire nuclear weapons.”