Iran is ready to resume negotiations with world powers on its nuclear programme, focusing on issues of "common ground," foreign ministry spokesman Ramin Mehmanparast said on Wednesday.

"We too are ready for useful dialogue and negotiation... which can be (based) on talks regarding cooperation on common ground," he was quoted as saying by the Mehr news agency.

"The principle of the start of negotiations is an important and positive issue for Iran," he told the ISNA news agency. "We have always announced our readiness for the negotiations."

Mehmanparast was responding to a letter sent last week by EU foreign policy chief Catherine Ashton.

In the letter, Ashton offered a resumption of the talks "in the next few weeks" between Iran and the so-called P5+1 -- UN Security Council permanent members Britain, China, France, Russia and the United States, plus Germany -- as long as Tehran imposed no preconditions.

The negotiations have been suspended since the beginning of the year.

They stalled after Tehran insisted that they also include the issues of broader nuclear disarmament in the Middle East and economic cooperation.

Iran's deputy foreign minister in charge of European and American affairs, Ali Ahani, on Tuesday said Tehran was preparing an official response to Ashton's letter, which he called "softer in tone" than previous communications.

Iran has so far refused to freeze its uranium enrichment activities, despite several UN sets of sanctions.

It has repeatedly denied US and EU allegations it is seeking to build an atomic bomb under cover of its civil nuclear energy programme.