The UN nuclear watchdog IAEA starts its board meeting from Monday with the Iranian nuclear issue still deadlocked but amid slight progress on Syria's disputed programme.

In its last report on Iran, the International Atomic Energy Agency, whose 35-member board of governors will meet from Monday to Friday in Vienna, said it had "new information" of possible military dimensions to Tehran's programme.

"Iran is not engaging with the agency in substance on issues concerning the allegation that Iran is developing a nuclear payload for its missile programme," it said, calling again for more cooperation.

For eight years now, the IAEA has been investigating Iran's nuclear programme to try to establish whether it is entirely peaceful as Iran claims or masks a covert drive to build a bomb as western powers believe.

How the agency should respond to Tehran's constant obstructions is the biggest challenge, as this behaviour, which Syria also seems to adopt, risks damaging the IAEA's credibility permanently, a Western diplomat said on condition of anonymity.

The UN Security Council has repeatedly asked Tehran to halt uranium-enrichment activities and a series of resolutions coupled with economic sanctions have had no effect so far.

Iran maintains it has the right under the nuclear Non-Proliferation Treaty to enrich uranium for electricity and medical purposes.

The concern is that, in highly refined form, enrichment can also produce the fissile core of an atom bomb.

According to the IAEA's report, Tehran informed the agency that it planned to have its second uranium enrichment plant in Fordow up and running "by this summer."

The construction of the Fordow plant in the country's southwest infuriated the West after Tehran admitted the site's existence in September 2009 and Iran was censured by the UN atomic watchdog over the issue.

While discussions over Iran's nuclear programme seem to be heading nowhere, the Syrian issue however appears to be making slow progress.

This week, diplomats said Damascus had agreed to a visit by IAEA inspectors for the first time since June 2008.

This "could represent a step forward," the watchdog noted.

The inspectors were on April 1 due to visit the nuclear site at Homs in the west of the country, which is known to the IAEA and is not thought to be suspect, a source close to the agency said.

The visit will not take in a possible uranium enrichment facility at Al Kibar, which was bombed by Israeli warplanes in 2007, the source added.

Details of the visit had yet to be finalised, the source said.

In November, IAEA chief, Japan's Yukiya Amano, sent a letter to Syria's foreign ministry demanding full cooperation, in what diplomats saw at the time as a sign of Amano's growing impatience.

Several states, including the United States, have been pushing for months for a possible IAEA resolution against Damascus or perhaps a so-called "special inspection," according to diplomats.