Chief nuclear inspector Mohamed ElBaradei is coming under intense pressure for his handling of the Iran file, with the United States and key allies accusing him of overstepping his authority, diplomats said Sunday.

The diplomats suggested that U.S. disenchantment with the International Atomic Energy Agency chief was at its highest since early 2005. That was when Washington actively considered pushing for his ouster because it considered him too soft on Iran and a drag on attempts to refer the Islamic republic to the U.N. Security Council — which finally happened last year.

Faced with majority support for ElBaradei among his agency's 35-nation board, the Americans dropped public opposition, and he was appointed for his third and final term in February 2005.

But U.S. displeasure was again aroused this year.

First ElBaradei suggested it was too late to expect Iran to scrap its uranium enrichment program — a key demand from Washington.

That provoked an informal warning in June to ElBaradei from a member of the U.S. mission to the IAEA — which he later withdrew — that Washington could launch a new attempt to oust him, said one of the diplomats, speaking on condition of anonymity in exchange for discussing confidential matters with The Associated Press.

Attempts to reach members of the U.S. mission for comment were unsuccessful Sunday, the eve of the start of an agency board meeting focusing on Iran.

Washington accuses Iran of wanting to build nuclear arms — something Iran's supreme leader, Ayatollah Ali Khamenei denied Sunday, saying his country had "no plans to create this deadly weapon."

In July, ElBaradei's agency displeased the Americans further by signing a deal with Tehran committing the Iranians to end years of stonewalling and answer questions about more than two decades of nuclear activities — most of it secret and some of it with possible links to a weapons program.

A report to be discussed by the board describes Iran's cooperation under the plan as "a significant step forward." But the U.S. continues to suspect that Iran is exploiting the plan as a smoke screen to deflect attention away from its continued defiance of a Security Council ban on enrichment, a potential pathway to nuclear arms.

The diplomats said Washington also feels that ElBaradei overstepped his authority by agreeing to such a deal without consulting the IAEA board.

But publicly, Washington and other nations backing new U.N. sanctions against Tehran have toned down initial criticism over the pact because they realized that opposition could backfire.

A diplomat said it could leave the impression that Iran's most vocal backers of new U.N. sanctions did not care about resolving the issue that had sent Iran's nuclear file to the Security Council in the first place — its refusal to cooperate in dispelling suspicions about past nuclear activities.

The Americans had sought to downplay differences as recently as Friday, with Gregory L. Schulte, the chief U.S. delegate to the IAEA, saying his country "appreciates and supports" IAEA efforts to glean information from Tehran.

At the same time, he said, Tehran "should suspend activities of international concern" — shorthand for enrichment.

ElBaradei himself has started hitting back. Also Friday, he disparaged the "Monday-morning quarterbacks" criticizing the Iran-IAEA cooperation plan without giving it enough time.

ElBaradei, who first incurred U.S. displeasure by challenging Washington's assertions of a nuclear weapons program in Saddam's Iraq, warned against "war-drums" rhetoric on Iran that is a "reminder of prewar Iraq." And he said calls for board involvement in agreements between the agency and one of its members — such as the cooperation pact — were "micromanagement."

Still the diplomats said that because of the pressure, the agency chief had agreed to stress the need for Iran to freeze enrichment in remarks at the board meeting opening Monday.

That commitment came after demarches — diplomatic expressions of protest — from the "pro-sanctions camp" about the IAEA-Iran pact and lack of board consultation on it, said one of the diplomats.

Some diplomats said the IAEA chief had also been subject to more insidious attacks in recent weeks, though they could not be certain these were linked to the diplomatic push against him.

Incidents included late-night threat calls to ElBaradei's residence and e-mails to representatives of board-member nations accusing him and other senior agency members of wrongdoing.

One e-mail, shared with the AP, says they are guilty of "abuse of power, arbitrary rule, widespread corruption, nepotism ... and violations of fundamental human rights." The e-mail purports to come from a former IAEA employee, but this could not immediately be verified.