Iran has so far ignored yesterday's informal deadline to respond to an offer by major powers on its nuclear programme, a European Union official said, but the bloc is ready to wait a few more days for an answer.

Major powers asked Iran on July 19 to respond within two weeks to their offer to hold off from imposing more UN sanctions if Tehran froze expansion of its nuclear work.

Iran dismisses the idea of having a deadline to reply and accuses the West of double standards.

"There is nothing new (from Iran)," the EU official said, adding that the bloc did not expect an answer over the weekend.

"One should not focus on the deadline too much... what matters is that we get a clear answer quickly, it's not a matter of one day," said the official, who spoke on condition of anonymity because of the sensitivity of the nuclear talks.

EU foreign policy chief Javier Solana leads the talks with Iran for the six major powers, the United States, China, Russia, Britain, France and Germany, who in June offered Iran economic and other incentives to halt uranium enrichment.

"It's unfortunate the Iranians have not responded to the P5+1's generous incentives package. It just further isolates their country," White House spokeswoman Dana Perino said yesterday, referring to the offer by the six major powers.

"We will be consulting with our allies," Perino said.

The West accuses Iran of seeking to build nuclear warheads under cover of a civilian power programme. Iran says its uranium enrichment drive is aimed purely at generating electricity and has vowed to press ahead on its nuclear path.

Iran's representative to the Vienna-based International Atomic Energy Agency (IAEA), Ali Asghar Soltanieh, said the country is open to talks but does not consider it is bound by any deadline to answer to the major powers' offer.