Thailand – The United States is concerned about the possible transfer of nuclear technology from North Korea to military-ruled Myanmar, U.S. Secretary of State Hillary Clinton said on Wednesday.

She also said complete and irreversible denuclearization was the only option for North Korea, saying after separate meetings with foreign ministers from China, Russia, Japan and South Korea that her counterparts supported this stance.

We have made it very clear to the North Koreans that if they will agree to irreversible denuclearization, that the United States as well as our partners will move forward on a package of incentives and opportunities including normalizing relations, Clinton told a news conference ahead of a regional security meeting in the Thai resort of Phuket.

Unless and until they do, they will face international isolation and the unrelenting pressure of global sanctions.

In an earlier television interview in Bangkok, Clinton expressed concern about links between Myanmar and North Korea.

Talk of Myanmar-North Korea military ties was fueled after a North Korean ship, tracked by the United States in June and July on suspicion of carrying banned arms, appeared headed toward Myanmar before turning around.

The threat that I have always worried about first and foremost is the proliferation of nuclear weapons and weapons of mass destruction, she said.

So obviously we are very concerned about North Korea and recent reports about perhaps their dealings with what we call Burma, she added. When asked specifically if she was worried about possible nuclear transfers to Myanmar, she said Yes.

The most contentious topics at the meeting of the ASEAN Regional Forum (ARF) on Thursday will likely be Pyongyang's nuclear program and how to promote democracy in Myanmar.

North Korea has a long history of arms proliferation and U.S. officials believe it helped Syria to build a nuclear reactor that was destroyed by Israeli bombers in 2007.

On Tuesday Clinton said she was worried about the possibility of military links between the two countries, both regarded as pariahs in the West.

North Korea and Myanmar are represented at the Phuket talks, although Pyongyang has only sent a low-level delegation.

A 2008 report from the International Atomic Energy Agency (IAEA) on member states' compliance with basic inspections agreements said Myanmar's declared nuclear material remained in peaceful activities.

But it noted Myanmar was among a handful states that had not adopted an additional protocol, which permits inspections beyond declared nuclear sites, enabling the U.N. watchdog to verify there are no secret proliferation activities going on.

SANCTIONS FIRST

U.S. officials earlier said Clinton would consult regional players in Phuket about giving North Korea a choice between tighter sanctions if it pursues its nuclear program and wider incentives if it abandons them.

In the last two months North Korea has conducted its second nuclear test, test-fired seven ballistic missiles and boycotted six-party talks on ending its nuclear programs in exchange for economic and diplomatic benefits.

U.S. officials said their main focus was to carry out U.N. Security Council resolution 1874, which bans all North Korean arms exports, authorizes U.N. member states to inspect North Korean sea, air and land cargo and requires them to seize and destroy any goods transported in violation of the sanctions.

However, they said they had discussed a wider package of incentives for the North from the other five parties if Pyongyang were to take credible steps on ending its nuclear program.

We would like to paint a picture for North Korea of a very stark choice, said one senior official who spoke to reporters on condition that he not be identified.

If they continue on the current path, it's a path that leads to greater tensions in northeast Asia, more isolation, more steps aimed at ... the regime, he added.

The official said the United States hoped to secure greater cooperation from its partners on sanctions if it showed that it was willing to be flexible about providing more incentives.

He declined to detail the incentives under consideration.

(Additional reporting by Jack Kim and Kittipong Soonprasert in Phuket and Mark Heinrich in Vienna; Writing by Dean Yates; Editing by Jeremy Laurence)