Thirty-five nations vote on Thursday for a new International Atomic Energy Agency chief at a time of mounting challenges to the nuclear non-proliferation regime, but it was unclear if a winner would emerge.

IAEA Director Mohamed ElBaradei, who shared the 2005 Nobel peace prize with his agency, leaves office in November after 12 years marked by rows with the ex-Bush administration over what he deemed aggressive U.S. policy toward Iraq and Iran.

His successor's mission to prevent the stealthy spread of nuclear weapons capability may benefit from a new U.S. diplomatic outreach under President Barack Obama to countries like Iran and Syria. Both are the target of unresolved agency investigations.

The vote by the U.N. agency's Board of Governors will pit Japan's ambassador, Yukiya Amano, favored largely by industrialized states, against South African counterpart Abdul Samad Minty, with core support among developing nations.

Diplomats said Amano, 62, had cemented a 6-10 vote lead over Minty, 69, and seemed closer than last month to the two-thirds margin in the IAEA's policy-making body needed for victory.

But an election stalemate remained possible, given at least half-a-dozen undecided delegations and chances for switching preferences tactically without detection in the secret ballot.

If the result is inconclusive, the race would be thrown open to new candidates for four weeks, followed by another vote. A new director must be chosen by June.

AMANO CONFIDENT

I have a good possibility of being elected this week. The reaction (to my campaign) has been very encouraging, Amano told Reuters. Minty said the number of last-minute fence sitters was important and no one should write off his chances.

Amano and Minty, both veterans of non-proliferation and disarmament posts and negotiations, each claim backing beyond their natural constituencies on the agency's Board of Governors.

But they have not bridged a schism between industrialized nuclear haves who stress the IAEA's watchdog remit -- inspections to deter diversions of nuclear technology into bomb making -- and nuclear have-nots who believe the IAEA must do more to spread the technology for energy development.

What's really missing here is a consensus candidate (in keeping with IAEA practice), said a diplomat close to the IAEA, who was not authorized to speak publicly on the delicate matter.

The Board is already polarized on all the big issues, so if you add the new director to the problem it makes things worse.

Broad backing from rich and poor nations is key to IAEA cohesion in a more precarious world -- Iran's disputed uranium enrichment drive, growing demand for nuclear power throughout the Middle East, and a need for more donor funding and legal authority to help the agency live up to its mission.

Amano has pledged to apply the mandate to forestall nuclear proliferators and promote peaceful uses of nuclear energy through technical cooperation in a balanced manner.

Western powers want the IAEA's next chief to stick to its mandate and be less political than ElBaradei, who they saw as inclined to be soft on Iran and to speak out of his box on matters of war and peace. He dismissed such accusations.

Western delegates think the low-key Amano would depoliticize the IAEA better than Minty, a former anti-apartheid activist identified with developing nation positions. But these nations, in turn, regard Amano as being too cozy with the United States.

Minty, an accomplished mediator with better communication skills than Amano, also promised an even-handed approach. He said, however, that the IAEA by its very nature has a political role since it reports to the U.N. Security Council.

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