WASHINGTON (AP) ― Little noticed in the warm glow of President Barack Obama’s landmark visit to Myanmar was a significant concession that could shed light on whether that Asian nation’s powerful military pursued a clandestine nuclear weapons program, possibly with North Korea’s help.

Myanmar announced it would sign an international agreement that would require it to declare all nuclear facilities and materials. Although it would be up to Myanmar to decide what to declare, it could provide some answers concerning its acquisition of dual-use machinery and military cooperation with Pyongyang that the U.S. and other nations regard as suspect.

President Thein Sein’s agreement to allow more scrutiny by U.N. nuclear inspectors suggests a willingness to go beyond democratic reforms that have improved relations with Washington and culminated in Obama’s visit this week, the first by a U.S. president to the country also known as Burma. 

David Albright and Andrea Stricker of the Institute for Science and International Security, a Washington-based nonproliferation group, said in an analysis it was a “remarkable decision.”

“This latest move by Burma is extremely positive for its ongoing push for openness about the nuclear issue and for building confidence and transparency with the international community,” they wrote.

However, there are also major doubts about how much Myanmar will divulge. Republican Sen. Richard Lugar, the most prominent voice in Congress on nonproliferation, said international concern would persist until Myanmar gives full disclosure of its relationship with Pyongyang.

After two decades of diplomatic isolation by the U.S., the Obama administration’s active engagement with Myanmar has encouraged the former pariah regime into making political reforms, reflected by opposition leader Aung San Suu Kyi’s election to parliament. Myanmar also agreed this week, after years of prodding, to open its notorious prisons to the International Committee of the Red Cross.

But until now, there has been little public indication of progress on security issues.

Secretary of State Hillary Rodham Clinton said during a visit last December that better U.S. relations with Myanmar would only be possible “if the entire government respects the international consensus against the spread of nuclear weapons.”

Myanmar denies there’s anything to worry about.

Last year, it declared it had halted plans to obtain a research reactor from Russia. That did little to allay worries of what might have happened under the radar. Anecdotal accounts suggest that around 2005, top leader Than Shwe had decided to seek North Korea’s help on a nuclear program.

Separately, about six years ago, Myanmar acquired precision machinery from Germany, Switzerland and Singapore that defectors and some analysts concluded were part of a half-baked attempt to make equipment for enriching uranium, although other experts disputed that conclusion.

Olli Heinonen, a former deputy director-general at the International Atomic Energy Agency, said the machinery, which could have nuclear or non-nuclear uses, was no smoking gun but raised questions. The end user certificates were signed by a head of Myanmar’s Department of Atomic Energy.

Heinonen, now a senior fellow at Harvard University’s Belfer Center for Science and International Affairs, said some countries had imposed restrictions on exports of special steels and other materials to Myanmar because of concerns they could be used for a nuclear program.

Lugar has voiced particular concern about Myanmar’s possible nuclear ties with North Korea. Photos of a 2008 trip by Thura Shwe Mann ― the Myanmar military’s joint chief of staff, now parliament speaker ―show him alongside Jon Pyong Ho, manager of North Korea’s military industry and chief operational officer behind the secretive country’s two underground nuclear tests in 2006 and 2009.

But the Obama administration has said the military trade between the two Asian nations appears to have been in small arms and missiles, in violation of current U.N. sanctions against North Korea.

According to the U.S. government, under a November 2008 accord North Korea agreed to help Myanmar build medium-range, liquid-fueled ballistic missiles. Two North Korean ships suspected to be heading to Myanmar with military cargoes in 2009 and 2011 were tracked by the U.S. Navy and turned around. And in July this year, even as the U.S. was easing investment restrictions on Myanmar, it sanctioned the country’s primary arms manufacturer, saying North Korean experts were active at its facilities.

Ben Rhodes, Obama’s deputy national security adviser, said Myanmar has taken “positive steps”toward severing its military ties with North Korea. He also welcomed Thein Sein’s agreement to sign the additional protocol with the IAEA, announced on the eve of Obama’s visit, saying it would bring Myanmar “into a nonproliferation regime that is important to the United States and the world.”

Myanmar’s current agreement with the IAEA requires little in terms of disclosure, and the government was unresponsive when the Vienna-based U.N. nuclear watchdog agency in late 2010 sought an inspection.

Albright and Stricker said Myanmar should answer questions the IAEA has about any past nuclear activities and the procurement of sensitive equipment. They also urged it to invite U.N. experts to visit the country and answer questions about past suspicious transfers and cooperation with North Korea.

But how quickly Myanmar moves to sign the protocol -- it says it first needs parliament’s approval -- and then ratify it, remains to be seen, as does whether it discloses any useful information.

“At the moment Burma has already been asked in public what they have and they say ‘nothing,’ so the list provided to IAEA could be short or blank,” said Robert Kelley, a former IAEA director who believes Myanmar has pursued a nuclear weapons program.

The military, which has dominated for five decades and also is heavily represented in Myanmar’s fledgling parliament, is likely to oppose scrutiny of sensitive sites.

“The concern of the international community will not pause until full disclosure of the North Korea-Burma relationship is achieved,” said Lugar.