Iran has ruled out any suspension of its uranium enrichment work, either as a precondition for talks with major powers or as part of their outcome.
Iran is embroiled in a worsening standoff with the United Stateds over its disputed nuclear program, which the US and others suspect is aimed at making atom bombs.
Tehran says it only wants to generate electricity.
"All ideas that put suspension as a base, either as a precondition or as a result of negotiations or during negotiations, are fundamentally not acceptable," a Foreign Ministry spokesman said this morning.
The comments came three days after senior officials from the United States, Britain, France, Russia, China and Germany met in Berlin to discuss Iran's refusal to halt uranium enrichment, as demanded by the UN Security Council.
Some diplomats said the Americans had been eager to discuss possible language for a new sanctions resolution during the Berlin talks.
The United Nations has imposed two sets of sanctions on Iran since December over its refusal to freeze enrichment - a process that can be used to make atomic warheads.
Iran's chief nuclear negotiator, Ali Larijani, also stressed on Friday that Tehran would not stop its atomic activities and said Western powers should not "waste their time".
Larijani is expected to meet European Union foreign policy chief Javier Solana later this month to resume talks on Iran's nuclear program though the exact place and date have not been announced.