VIENNA - The UN nuclear watchdog's annual conference started Monday with a showdown looming over efforts by Syria and Iran to get a seat on the IAEA board and Islamic countries railing against Israel's nuclear programme.

The International Atomic Energy Agency's 145 member countries gathered in Vienna for the 52nd general conference, an annual week-long meeting for drawing up general policies on a whole range of issues, from non-proliferation, nuclear terrorism to medical applications of nuclear technology.

This year, however, proceedings look set to be dominated by two key issues: the possible candidature of either Syria or Iran for a seat on the IAEA's 35-member board; and Islamic countries' anger over Israel's nuclear weapons.

Israel is widely believed to be the only country in the Middle East to possess nuclear arms, but it refuses to open up its programme to international inspections.

In the past two years, Islamic countries have put a resolution urging all Middle East nations to refrain from testing or developing nuclear arms. It urges nuclear weapons states "to refrain from any action" hindering a Middle East nuclear-free zone.

Last year, they even singled out Israel as a "nuclear threat" in a separate resolution.

Angered at the move, Israel put the resolution to a vote and the resolution was duly defeated.

Nevertheless, the issue could come to a head again this year, since Arab states have again tabled an item this time entitling it "Israeli nuclear capabilities".

Diplomats said Israel could again force a vote on the Middle East nuclear-free zone resolution unless the second item is withdrawn.

The next key issue looks set to be the candidature of Iran and Syria for a possible seat on the IAEA board, much to the consternation of Western states.

Board members are designated and elected each year by the general conference.

And a seat is set to become free this year with the expiry of Pakistan's one-year term.

The seat is to be allocated to another country within the so-called Middle East and South Asia (MESA) group. Diplomats close to the IAEA have told AFP there are four possible candidates: Iran, Syria, Afghanistan and Kazakhstan.

MESA has until the end of the general conference to decide on a single candidate and the choice is normally adopted by consensus.

The problem is that both Iran and Syria are currently in the dock over their purported clandestine nuclear work. Their nomination would almost certainly run into resistance if MESA decided to choose either of them, diplomats said.

And that could mean that a vote would have to be called at the conference, unprecedented in the IAEA's history.

The IAEA has been investigating Iran's contested nuclear programme for the past five years, but has so far been able to determine whether the activities are entirely peaceful as Tehran claims.

Western powers accuse the Islamic republic of using technology for nuclear energy as a guise to build an atomic bomb.

The United Nations Security Council has slapped three rounds of sanctions on Iran over its refusal to come clean about its nuclear programme and its refusal to cede to international demands to cease uranium enrichment. This process can be used to make the fissile material for a nuclear bomb.

Syria, which last sat on the IAEA's board in 2006, is also at the centre of controversy. The United States has alleged it was building a covert nuclear facility at a remote desert site called Al-Kibar until it was destroyed by Israeli bombs in September 2007.

Damascus allowed a three-member team from the IAEA to visit Al-Kibar in June, but has since refused any follow-up visit. A diplomat close to the IAEA told AFP on Friday that an official request to visit "three or four" other sites allegedly involved in clandestine nuclear activities had so far gone unanswered.

Speaking on condition of anonymity, diplomats said that the United States would not be happy if MESA decided to name either Syria or Iran as their candidate for a seat on the board.

Thus, Western states were hoping that MESA would choose a candidate that would allow the nomination to be adopted by consensus, "that is to say, neither Syria nor Iran," one diplomat said.