U.S. Secretary of State Hillary Clinton said Tuesday that the Obama administration is concerned by the possibility that North Korea, with a history of illicit sales of missiles and nuclear technology, may have military ties to Burma.

She did not refer explicitly to a nuclear connection but made clear that the matter is worrying.

"We know there are also growing concerns about military cooperation between North Korea and Burma which we take very seriously," she said when asked about the matter at a news conference in the Thai capital.  Burma, also known as Myanmar, is run by a military regime.

"It would be destabilizing for the region, it would pose a direct threat to Burma's neighbors," she said, adding that as a treaty ally of Thailand, the United States takes the matter seriously.

Later, a senior administration official said Washington is concerned about the possibility that North Korea could be cooperating with Burma on a nuclear weapons program, but he added that U.S. intelligence information on this is incomplete. The official spoke on condition of anonymity because of the sensitive nature of the matter.

Another administration official, speaking under the same ground rules, said one reason for concern on the nuclear front is the evidence that North Korea helped Syria clandestinely build a nuclear reactor, which was later destroyed in an airstrike by the Israeli air force.

Clinton spoke to reporters after meeting with Thai Prime Minister Abhisit Vejjajiva at the outset of a three-day visit to Thailand. She is scheduled to fly to the Thai seaside resort of Phuket on Wednesday to attend an international meeting on Asian security. Burma and North Korea are expected to have representatives there, but Clinton has no plans to meet with them, officials said.
At the news conference, Clinton held out the possibility of enticing North Korea back to negotiations on reversing its nuclear program.

"We think that there is a different path for North Korea to follow, that there is an opportunity which is theirs for the taking, but they have to be willing to change their behavior and agree to de-nuclearize North Korea, which would mean that the entire Korean peninsula is denuclearized, and we stand ready to respond if we get any signal that there would be a serious commitment to doing that," she said.

The senior administration official said the U.S. has not yet received any such signal from Pyongyang.