Iran and the United Nations nuclear watchdog will have further talks over Tehran's disputed nuclear program around May 21 in Vienna, Iranian media reported on Monday.

There was no immediate confirmation from the International Atomic Energy Agency (IAEA), leaving unclear whether a firm date for the next meeting had already been agreed.

Iran's Mehr and ISNA news agencies initially reported that the meeting would be held on May 21, but ISNA later quoted an unnamed official as saying this was only a "preliminary agreement" and that the date could be moved by one or two days.

The IAEA-Iran talks are separate from, but have an important bearing on, diplomatic negotiations between Tehran and six world powers aimed at a broad settlement to the decade-old dispute to head off the risk of a new Middle East war.

Western powers suspect Iran is trying to develop the capability to produce nuclear weapons under the guise of a declared civilian atomic energy program. Iran denies this, saying it seeks only electricity from uranium enrichment.

But its refusal to curb sensitive nuclear activity with both civilian and military applications and its lack of openness with IAEA inspectors have drawn U.N. and Western sanctions.

Last week, a diplomatic source told Reuters that a meeting between the Vienna-based IAEA and Iran in May was a possibility, but that no date had yet been fixed.

If it were to take place, it would be the 10th round of negotiations between the two sides since early 2012, so far without a deal that would enable the U.N. watchdog to resume its long-stalled investigation into Iran's nuclear facilities.

A Western diplomat in Vienna held out little hope the next round of talks would be more successful than previous rounds.

If confirmed, it would take place shortly before the IAEA is expected to issue its next quarterly report on Iran's nuclear program and ahead of a June 3-7 meeting of the IAEA's 35-nation, policymaking Board of Governors, when the Iranian nuclear dispute will once again be on the agenda.

"We have seen this game before," said the diplomat, from a Western country critical of the Islamic Republic.

"Iran seems to have no intention of engaging in real dialogue...(It) just maintains the illusion of movement in order to deflect tough responses from the international community."

Officials at Iran's IAEA legation were not immediately available for comment. The last round of IAEA-Iran negotiations, in February, yielded no breakthrough.

Speaking in Geneva on Monday, European Union nuclear non-proliferation official Jacek Bylica said the EU was "deeply concerned" about Iran's nuclear program.

"Our objective remains to reach a comprehensive long-term settlement, which would restore international confidence in the exclusively peaceful nature of Iran's nuclear program," Bylica said, according to a prepared statement.

Some analysts say the Islamic Republic's leadership may be unwilling or unable to make important decisions in nuclear negotiations before its presidential election in June. (For an interactive timeline on Iran's nuclear program, click on link.reuters.com/gad76r)