VIENNA, Austria — 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 yesterday, urging Iran to reassure the world by ending its secretive ways.

At the opening session of the International Atomic Energy Agency’s 145-nation conference, the European Union also urged Tehran to cooperate fully with a U.N. probe that is trying to assess all of its past and present nuclear activities.

“The international community cannot accept the prospect of Iran acquiring nuclear weapons,” the European Union said in a statement.

Israel also took Iran to task for co-sponsoring Islamic attempts to label the Jewish state a nuclear danger to the Middle East.

“What moral standing poses sponsors of this agenda item, who do not recognize Israel’s right to exist while criticizing Israel policies aiming at securing its very existence?” an Israeli delegate, Schaul Chorev, asked.

He was alluding to President Ahmadinejad’s call for Israel to be wiped off the map.

Iran, in turn, accused America, Britain, and France of breaking their nonproliferation commitments by giving Israel “full uninterrupted cooperation with, and assistance in, nuclear weapon technology.”

Tehran’s delegate, Ali Ashgar Soltanieh, also condemned the “illegal and unjustified engagement of the United Nations Security Council” in pressuring his country to suspend uranium enrichment — something he said would never happen.

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

Tehran was running to counteract an American 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 reportedly destroyed last year by Israel.

But both Iran and Kazakhstan withdrew their candidacies by evening, Syria’s chief representative to the IAEA, Mohammad Badi Khattag, said. “There is near consensus in our group for us,” he told the Associated Press. “Nobody supports Afghanistan, except Afghanistan.”

Still, if the regional group did not agree on a candidate, the full conference would be asked to vote on which nation should take the board seat.

In his opening speech, the IAEA’s director, Mohamed ElBaradei, 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.