A six-year probe has not ruled out the possibility that Iran may be running clandestine nuclear programs, the chief U.N nuclear inspector said Monday, urging Iran to reassure the world by ending its secretive ways.

Europe also urged Tehran to fully cooperate with a U.N probe that is trying to assess all of its past and present nuclear activities. An EU statement on the opening session Monday at the International Atomic Energy Agency's 145-nation conference declared: "The international community cannot accept the prospect of Iran acquiring nuclear weapons."

Iran, along with ally Syria, figures directly at the Vienna conference because they are among four nations seeking their geographic region's nomination for a seat on the IAEA's decision-making 35-nation board.

Iran's bid is strategic. Tehran is running to counteract a U.S. push to have Afghanistan or Kazakhstan elected over Syria, which is under IAEA investigation for allegedly hiding a secret nuclear program, including a nearly completed plutonium producing reactor destroyed last year by Israel.

If the regional group does not agree on a candidate, the conference will be asked to vote on which nation should take the board seat.

In his opening speech, chief U.N nuclear inspector Mohamed ElBaradei, the head of the IAEA, focused on Iran's refusal to suspend its uranium enrichment program and alleged past plans to develop the bomb.

The U.N. Security Council approved a resolution Saturday critical of Tehran's defiance on uranium enrichment, which can create both nuclear fuel and the fissile core of warheads.

Urging Iran to "implement all transparency measures ... required to build confidence in the exclusively peaceful nature of its nuclear program," ElBaradei declared: "This will be good for Iran, good for the Middle East region and good for the world."

He also warned the session that his organization is increasingly stretched in trying to carry out responsibilities that include nonproliferation and preventing terrorists from acquiring the bomb.

"All is not well with the IAEA," ElBaradei declared, appealing for greater financial support and more authority for his agency.

The annual meeting allows the agency's member countries to set policies that range from strengthening nonproliferation to carrying out medical and scientific research. But tensions between Islamic members and the West threaten to hamper decision-making at this session.

The tradition of consensus has normally led all sides to bridge sometimes substantial differences and opt for compromise for most of the conference's 52-year history. A vote on any topic is unusual and considered a huge dent in the meeting's credibility.

But frustration among Muslim countries over Israel's refusal to put its nuclear program under international purview, and resistance from the Jewish state to Muslim pressure on the issue, threatens to force a vote for the third year running.

As in the past two years, Muslim IAEA members were expected to put forward a resolution urging all Mideast nations to refrain from testing or developing nuclear arms and urging nuclear weapons states "to refrain from any action" hindering a Mideast nuclear-free zone.

After losing the vote two consecutive years, Islamic nations are threatening to up the ante this year, warning they will call for a ballot on every item, no matter how uncontroversial, unless they get conference backing on the Israeli nuclear issue.

Arab members — backed by Iran — this year have again asked conference organizers to include an item on Israel — a move being protested by Israel.

Focusing on Israel by name "is substantially unwarranted and flawed," said a letter prepared for review by the conference from Israel Michaeli, the Jewish state's IAEA representative.

Sponsors of the item should instead "address the most pressing proliferation concerns in the Middle East," the letter said, an allusion to Iran's defiance of U.N. Security Council sanctions for refusal to stop uranium enrichment.

A draft of the document made available to The Associated Press "expresses concern about the Israeli nuclear capabilities" and urges the Jewish state to throw its atomic activities open to full IAEA view.

Dozens of nuclear organizations are using the meeting to stage events of their own. One of them, the Washington-based Nuclear Threat Initiative, launched a new organization, the World Institute for Nuclear Security, which aims to prevent terrorists from getting the bomb by providing a forum for nuclear specialists.

"If we didn't have WINS we should have invented it, because it fills an urgent gap in our need to strengthen the (nuclear) security system," said ElBaradei.