Q+A: What is at stake in Israel row at UN atom body?

VIENNA (Reuters) - Member states of the U.N. nuclear watchdog debated an Arab-proposed resolution on Friday calling on Israel to join a global anti-nuclear arms pact, and were expected to vote on the measure later in the day.

Washington warns that singling out Israel at the International Atomic Energy Agency (IAEA) may upset broader efforts to ban weapons of mass destruction in the Middle East, as well as the revived Israeli-Palestinian peace talks.

Arab diplomats argue Israel's presumed nuclear arsenal is a threat to regional security. They say their draft IAEA resolution calling on the Jewish state to accede to the Non-Proliferation Treaty (NPT) could advance peace moves.

Israel, which would have to renounce nuclear weaponry if it signed the pact, condemns the non-binding Arab resolution as a politically motivated bid to divert attention from what it sees as the region's main proliferation threats -- Iran and Syria.

On Tuesday at the IAEA, a senior Israeli official condemned what he called "continuous ill-motivated efforts to single out and to condemn" his country.

Director General Shaul Chorev of Israel's Atomic Energy Organization said the "proposed resolution is incompatible with basic principles and norms of international law."

The following looks at the debate, which has dominated negotiations on the sidelines of the week-long, annual assembly of the 151-member IAEA in Vienna.

WHAT IS ISRAEL'S NUCLEAR STATUS?

Israel -- like India, Pakistan and North Korea -- is outside the NPT. It is believed to have the Middle East's only atomic arsenal, with an estimated 80-200 warheads, though it has never confirmed or denied this. Unlike the other three NPT outsiders, it has never publicly tested nuclear devices.

This policy of ambiguity, used to deter regional foes, means it does not have to open up all of its atomic sites to the IAEA.

But it also means Israel does not receive all the help it could get under the NPT to build up civilian nuclear power.

The 40-year-old global treaty is the cornerstone of nuclear disarmament efforts and is at the heart of the IAEA's work. It received strong backing from U.S. President Barack Obama at a milestone review conference in May.

Israel says it won't consider joining the NPT until there is comprehensive Middle East peace. Arab states say there cannot be such peace until the Jewish state gives up its nuclear arsenal.

Israel is unlikely to agree to join a nuclear weapons-free zone in the Middle East "as long as there is no peace agreement between Israel and all its Arab neighbors and as long as there is a chance of Iran becoming a military nuclear power," said Nicole Stracke of the Gulf Research Center in Dubai.

Israel has two nuclear reactors -- the secretive Dimona facility in the Negev desert, where it is assumed to have produced nuclear weapons, and a research reactor, open to IAEA inspection, at Nahal Soreq near Tel Aviv.

It has also started a feasibility study for a nuclear power plant.

WHY DOES THE ARAB RESOLUTION MATTER?

Arab states are seeking to build on a victory at last year's IAEA meeting when they narrowly won backing for a resolution on "Israeli Nuclear Capabilities," after 18 years of attempts. They have put forward a similar text this year.

Israel sees the resolution as driven by its enemies. The United States, its main ally, says the resolution is unfair and divisive and calls for it to be withdrawn.

Washington says it could undermine an Egyptian-proposed conference in 2012 toward establishing a Middle East zone free of weapons of mass destruction, suggesting Israel would be unlikely to take part if targeted by Arab states at the IAEA.

IAEA Director General Yukiya Amano, in a speech opening the assembly on Monday, said he hoped the 2012 meeting "will take place with the participation of all relevant states and that it will lead to a productive outcome." Arab states have accused him of not pressing Israel hard enough to join the NPT.

U.S. officials also warn the Arab resolution would have a negative impact on the Israeli-Palestinian peace negotiations.

"It would do nothing but send a negative signal to the larger peace process," U.S. envoy Glyn Davies said.

But Mikhail Wehbe, Arab League Representative to the IAEA, said: "We believe this resolution supports the peace process."

Nuclear expert Mark Hibbs at the Carnegie Endowment for International Peace said approval of the resolution would be a U.S. setback but it would not derail the peace process.

"Of course, if Israel wants to walk away from both the 2012 conference and the peace process, it will claim that the Arabs' call for Israel to join the NPT set both tracks back," he said.

WHAT COULD HAPPEN AT THE IAEA?

The 2009 resolution was approved with a 49-45 margin majority, backed mainly by developing countries.

The United States, which dispatched its senior nuclear adviser Gary Samore to the IAEA last week to meet Arab envoys, has lobbied hard against a repeat this year and diplomats say another Arab victory is far from certain in any new vote.

Arab diplomats say they are open for dialogue, while making clear they won't drop the demand that Israel sign up to the NPT.

Once a resolution is formally put forward to the assembly it can only be withdrawn if all its sponsors agree to do so, making it more difficult to find a possible compromise.

(Reporting by Sylvia Westall and Fredrik Dahl; Editing by Mark Heinrich)