The head of the United Nations atomic watchdog is asking for international input on how to persuade Israel to join the Nonproliferation Treaty, in a move that is sure to add to pressure on Israel to disclose its unacknowledged nuclear arsenal.

In a letter made available Wednesday, Yukiya Amano asked foreign ministers of the International Atomic Energy Agency's 151 member states to share views on how to implement a resolution demanding that Israel accede to the Nonproliferation Treaty and throw its nuclear facilities open to IAEA oversight.

The letter was shared with the Associated Press amid renewed Arab criticism of Israel during an international conference at UN headquarters in New York.

Islamic nations used the second day of the nonproliferation meeting Tuesday to call for a nuclear-free Middle East, while criticizing Israel for not divulging its nuclear capabilities and refusing to sign the nonproliferation treaty.

Egypt has proposed that this 2010 Nonproliferation Treaty conference back a plan calling for the start of negotiations next year on a Mideast free of nuclear arms. The proposal may become a major debating point in the month-long session.

The U.S. has cautiously supported the idea while saying that implementing it must wait for progress in the Middle East peace process. Israel also says a comprehensive Middle East peace settlement must come first.

Amano's April 7 letter comes seven months after IAEA member states at their annual conference narrowly passed a resolution directly criticizing Israel and its atomic program, with 49 of the 110 nations present backing the document, 45 against and 16 abstaining.

The result was a setback not only for Israel but also for Washington and other backers of the Jewish state, which had lobbied for 18 years of past practice - debate on the issue without a vote. It also reflected building tensions between Israel and its backers and Islamic nations, supported by developing countries.

The resolution expresses concern about the Israeli nuclear capabilities, and links it to concern about the threat posed by the proliferation of nuclear weapons for the security and stability of the Middle East.

The U.S. and its allies consider Iran the region's greatest proliferation threat, fearing that Tehran is trying to achieve the capacity to make nuclear weapons despite its assertion that it is only building a civilian program to generate power.

But Islamic nations insist that Israel is the true danger in the Middle East, saying they fear its nuclear weapons capacity. Israel has never said it has such arms, but is universally believed to possess them.

The Muslim countries enjoy support from developing nations. These are critical of the U.S. and other nuclear weapons nations for refusing to disarm, and suspects that developed nations are trying to corner the market on peaceful nuclear technology to their disadvantage - themes likely to surface not only at the now ongoing Nonproliferation Treaty conference, but at the next IAEA general conference in September.

With divisions deep on Israel, Amano's letter asking IAEA member states for input on the issue foreshadowed intense feuding at that September conference.

"It would be helpful to me if Your Excellency could inform me of any views that your government might have with respect to meeting the objectives of the resolution," according to his half-page letter.

A senior diplomat from one of the IAEA member countries confirmed that his government had received the letter. He and an official from another IAEA delegation said that to their knowledge the agency was still awaiting responses. Both asked for anonymity because their information was confidential.