WASHINGTON - US DEFENCE Secretary Robert Gates heads to Asia on Wednesday to sound out regional leaders over tensions raised by a North Korean nuclear test and its threat to attack South Korea, a US ally.

In Singapore, the Pentagon chief will take part in a three-way meeting with his Japanese counterpart, Mr Yasukazu Hamada, and South Korean Defence Minister Lee Sang Hee.

In a sign of the escalating tensions two days after Pyongyang announced it had tested a nuclear weapon, the communist regime said on Wednesday it regarded South Korea's decision to join a US-led counter-proliferation initiative as 'a declaration of war'.

Secretary of State Hillary Clinton quickly reacted by promising to honour US commitments to defend South Korea and Japan.

'Both of our allies that are closest to North Korea have significant concerns,' said another senior defence official, who spoke on condition of anonymity.

The official said the United States wanted to 'jointly work together on what the proper response should be,' as the UN Security Council considers sanctions against North Korea. 'We want to work with Asia on Asia's problems,' the official said.

Mr Gates will use the eighth annual Shangri-La Dialogue, organised by the International Institute for Strategic Studies, to emphasise President Barack Obama's desire to engage the region, which Mrs Clinton visited in February.

Mr Gates is expected to meet in Singapore with a senior Chinese military official. He also will have bilateral meetings with his counterparts from Vietnam, Indonesia, Singapore, New Zealand, and Mongolia.

Mr Gates will travel on Sunday to the Philippines, where some 600 US soldiers are training and providing support to the Philippines military in their campaign against Communist New Peoples Army rebels in the south of the country. -- AFP