But there is no guarantee of a vote as the United States strongly opposes what would be a third four-year term for ElBaradei, who is 62. Washington considers the Egyptian-origin diplomat not tough enough on Iran, which the United States charges is hiding a covert nuclear weapons program, diplomats said.

The decision on a new director general of the International Atomic Energy Agency could still be put off until a regular IAEA meeting in June, as there is time since ElBaradei's term expires in November, diplomats said.

Developing nations at the IAEA are pushing for a decision however "as there is a restive feeling the process has gone on too long as there is a candidate and almost no one is opposed to him," a diplomat from a non-aligned nation, who asked not to be named, told AFP.

The notification of the extraordinary IAEA meeting in April of the agency's 35-nation board of governors was made Tuesday by Canadian ambassador and current board chair Ingrid Hall to all 137 IAEA members.

The deadline for submitting candidacies fell last December 31.

The IAEA board elects the director general by a two-thirds vote with the final ratification coming at an IAEA plenary conference in September.

Washington justifies its stance against ElBaradei, who has run the IAEA since 1997, on the grounds that agency heads should not serve more than two terms, in line with a policy set by a Geneva group of top 10 contributors to UN organizations.

But Hall had told an IAEA board meeting in March that "ElBaradei has strong and broad support," according to a Western diplomat.

The diplomat said the "board is waiting for the United States to accept that there is only one candidate and that he has the board's backing."

Hall has received letters from Argentina and Algeria on behalf of the Group of 77 and China, Latin American and Caribbean states as well as African states in support of ElBaradei, according to copies of the letters obtained by AFP.

Hall said in her statement Tuesday that the April 27 board meeting was being held "as requested by the Group of 77 and China."

Indonesian ambassador T.A. Samodra Sriwidjaja said in letter to Hall on behalf of the group, and dated March 31, that as Hall had said in March "the issue should not be allowed to linger."

Sriwidjaja said "the delay in dealing with this could be disruptive to the agency."

In another letter earlier this year, Algerian ambassador Taous Feroukhi, had said the IAEA's "prestige and credibility are at an all-time high" and this is "due to the effective leadership and sound management provided by the present director-general."

ElBaradei also has support from European states, which back a policy of urging Iran to cooperate rather than confronting it as Washington has sought.

The United States, meanwhile, is having trouble finding "a good competing candidate," a second Western diplomat told AFP, and reportedly failed last year to convince Australian Foreign Minister Alexander Downer to put himself forward.

The United States "can still block ElBaradei with 13 votes but the challenge remains to find another candidate," the diplomat said, referring to the two-thirds vote.

The diplomat said the United States felt it still had three weeks to go before the board meeting and will "be trying to build a blocking third" of votes or to get the issue to be put off until June for procedural reasons.

"Policymakers in Washington believe there is still time enough on this issue," the diplomat said.

The United States wants the IAEA to report Iran to the UN Security Council for possible sanctions but ElBaradei says the "jury is still out" on whether Tehran's program is peaceful or not.

ElBaradei has also earned the ire of Washington by questioning US intelligence that Iraq had weapons of mass destruction under now deposed dictator Saddam Hussein.

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