Among the hundreds of thousands who have fled Myanmar and its tyrannical rulers over the years is a military insider who claims he carried a big secret with him: evidence of a hidden nuclear weapons program.

Defector Sai Thein Win's account of his three years working in two clandestine factories, even with the trove of photos he brought with him, is no smoking gun. It has deepened suspicions, however, that Myanmar's xenophobic military leaders hanker for an atomic deterrent.

His allegations touch on a matter that is bound to resurface as Myanmar, also known as Burma, tries to curry international favor and end sanctions. While human rights and democracy have dominated Western attention to Myanmar, there also have been misgivings about its growing ties with North Korea, a suspected nuclear proliferator that may have exported missile technology to Myanmar.

In late May, a U.S. Navy destroyer intercepted a North Korean ship, suspected to have been carrying a cargo that violated U.N. nonproliferation sanctions, U.S. officials say. A Washington-based foreign diplomat, speaking on condition of anonymity because of the sensitivity of the matter, said the cargo was suspected to have been weapons or missiles headed for Myanmar. The ship turned back to North Korea.

Myanmar has tried to ease international suspicions that it has illicit nuclear programs. Two weeks ago, after a visit by Sen. John McCain, R-Ariz., it announced that it was abiding by the U.N. sanctions. The government also said it had halted arrangements for nuclear research with Russia for its educational and health sectors. It said the "international community may misunderstand Myanmar over the issue."

In fact, the plans to build a research reactor with Russian help, first raised in 2000, never got off the ground, apparently because of payment problems and because Myanmar, a signatory to the nonproliferation rules of the International Atomic Energy Agency, has failed to sign an additional IAEA protocol with the U.N. watchdog for monitoring such a program.

Perhaps of greater concern is what Myanmar may have been pursuing completely under the radar.

Sai Thein Win, 35, has provided the most persuasive proof to date of a secret nuclear program. Such allegations have swirled for years but are hard to substantiate and are treated with some skepticism because of Myanmar's dearth of trained physicists and technicians.

Sai Thein Win, an army major and mechanical engineer, left Myanmar in February 2010 and appeared in a hard-hitting documentary filmed by the Democratic Voice of Burma, an exile media network. Myanmar swiftly denied it was seeking nuclear weapons, but its condemnation of the defector as an army deserter verified that he had served in the military and had undertaken postgraduate engineering studies in Russia.

He spent five years at Moscow State Technical University studying liquid-fueled rocket engine design for missiles. He recounted to The Associated Press that before leaving for Russia, he attended a May 2001 address to some 300 officers by Myanmar's then second-ranking general, Maung Aye, at the National Defense College in Yangon.

"He said they wanted us to study about rockets and nuclear reactors. They also said they needed weapons and long-range missiles to protect the country," Sai Thein Win said.

After returning to Myanmar, he worked for a year in a military research center, which managed the nuclear effort. He then spent three years at two factories in the western township of Myaing and in the northern township of Pyin Oo Lwin that he says attempted to make equipment for an intended uranium enrichment program using precision machinery from Germany and Singapore.

He said he initially believed in the program he worked on but became increasingly disillusioned. He said it was badly managed and a waste of money, driven by the ruling generals' thirst for power, and it was destined to fail.

"They knew what they wanted but did not know how to achieve it," he said in an interview from an undisclosed exile location that he does not want disclosed because of fears for his safety.

Experts have been divided on whether Sai Thein Win's account, including hundreds of photos of factory sites and manufactured components, amounts to proof that Myanmar was seeking nuclear weapons technology.

Robert Kelley, a former IAEA director and nuclear weapons inspector who interviewed Sai Thein Win and assessed the evidence he provided for the 2010 documentary, is confident it does, although engineering drawings were unprofessional and the manufactured items appeared crude. The method identified for enriching uranium, molecular laser separation, was highly unlikely to succeed.

David Albright, an analyst at the Institute for Science and International Security think tank and a former U.N. weapons inspector, concluded there could be non-nuclear applications. He wrote that it was impossible to discern whether a vital piece of equipment known as a bomb reactor was intended to produce uranium or some other metal instead.

Albright also questioned the credibility of information from defectors who could have a political ax to grind against Myanmar's rulers.

Still, the International Atomic Energy Agency has indicated an interest in interviewing Sai Thein Win, although it is unclear why it has failed to do so since he defected 15 months ago. Gil Tudor, a spokeswoman for the Vienna-based agency, said in an email to The Associated Press that the IAEA had taken steps to contact Sai Thein Win but has not been able to speak to him yet.

Sai Thein Win says that since he left Myanmar, no foreign government or agency has debriefed him.

The U.N. nuclear watchdog has been sufficiently concerned about allegations over Myanmar's nuclear activities that several months ago it requested a meeting and inspection of a particular site in the country. Tudor would provide no details about that site but said Myanmar has yet to respond.

U.S. officials say they worry that Myanmar could be seeking nuclear and missile technology, and the United States closely monitors its trade with North Korea, which allegedly helped Syria build a reactor that was bombed by Israel in 2007. Military trade with North Korea is forbidden under U.N. sanctions imposed in 2009 after its nuclear and ballistic missile tests.

U.S. officials believed North Korea may have reached an agreement with Myanmar to provide it with ballistic missile technology, according to a U.S. diplomatic cable dated October 2009 that was leaked to the WikiLeaks organization and subsequently obtained by the AP. Other reports suggest North Korea has sold Scud missiles to Myanmar.


Associated Press writer Grant Peck in Bangkok, Thailand, contributed to this report.