Iran and six world powers are expected to resume in the next few weeks long-stalled talks about the Islamic state's disputed nuclear programme, diplomatic sources said on Tuesday.

One Western diplomat said he expected a meeting to be held on April 13-14, while another envoy said those dates had not been confirmed and a third suggested later in the month was possible. The venue was unclear, they said.

A spokesman for European Union foreign policy chief Catherine Ashton, who handles dealings with Iran on behalf of the big powers, said nothing has been decided yet regarding the time and place for a meeting.

The last meeting over the nuclear work that Iran says is peaceful but the West suspects has military links took place in Istanbul in January 2011, when the two sides failed even to agree on an agenda.

It is hard to be optimistic given Iran's track record at previous talks, one Western diplomat said when asked about the prospects for progress in the dispute.

Two weeks ago, Iran welcomed new nuclear negotiations with six world powers - the United States, Russia, France, Germany, Britain and China - saying the two sides should set the date and venue of the talks.

That overture came a week after Ashton accepted Iran's offer of further discussions in a bid to reach agreement on the future of Iran's nuclear activities.

Ashton would lead the talks with Iran on behalf of the six powers, which earlier this month called on Iran to enter, without pre-conditions, into a sustained process of serious dialogue, which will produce concrete results.

Iran has repeatedly rejected Western accusations that its nuclear energy programme is a cover for developing nuclear weapons, saying its goals are entirely peaceful, and has ruled out suspending uranium enrichment.

The United States and the EU have imposed tough sanctions on Iran's banking and energy sectors in an effort to pressure it to abandon the uranium enrichment programme, which can have both civilian and military purposes.

(Reporting by Fredrik Dahl in Vienna and Sebastian Moffett in Brussels; Editing by John Stonestreet)