BRUSSELS (AP) — Representatives of six world powers urged Iran today to accept a U.N. plan aimed at delaying its ability to build a nuclear weapon, as the head of the U.N. nuclear watchdog agency warned Tehran not to miss the opportunity to resolve the dispute.

An EU official said there was no mention of imposing sanctions against Iran for its refusal to halt nuclear enrichment activities at the meeting of senior diplomats from the U.N. Security Council’s five permanent members plus Germany.

“These things are a matter of timing, and this was not the right time for it,” said the official who asked not to be named because of the sensitivity of the matter.

The talks in Brussels involved political directors — foreign ministry officials below ministerial level. The United States was represented by Undersecretary of State William Burns, and Russia by Deputy Foreign Minister Sergei Ryabkov.

The talks came just a day after President Barack Obama said the six nations will develop a package of serious new punitive measures in coming weeks.

On Wednesday, Tehran indicated it would not export its enriched uranium for further processing.

In Berlin, Mohamed El-Baradei, the U.N. nuclear watchdog agency chief, pressed Iran to work with the international community.

“I would hate to see that we are moving back to sanctions,” El-Baradei said. “Because sanctions, at the end of the day ... really don’t resolve issues.”