Communist allies North Korea and China proclaimed their unity Thursday as the North's leader Kim Jong-Il held his first meeting with a senior Chinese envoy since the region's worst crisis in years erupted.

China's most senior foreign policymaker Dai Bingguo visited Pyongyang as pressure intensifies on Beijing to rein in its neighbour, after North Korea's deadly shelling of a South Korean island inflamed tensions on the peninsula.

The top US military officer, Admiral Mike Mullen, accused China of aiding and abetting the hardline Kim regime's "reckless behaviour".

Pyongyang and Beijing, allies during the Korean War, stand firmly together, their official media said.

"The two sides reached consensus on bilateral relations and the situation on the Korean peninsula after candid and in-depth talks," said a brief report from China's Xinhua news agency, datelined Pyongyang, after Kim and Dai met.

North Korea's official news agency said the delegations discussed "issues of mutual concern" and efforts to improve friendly relations.

It marked the first time that Kim has met a senior foreign official since the North's shock artillery attack on the border island, and since his regime startled the world by showing off a sophisticated new nuclear programme.

China is North Korea's sole major ally and sustains its shaky economy with fuel and food aid.

But Beijing has come under increasing pressure from the United States and US allies to rein in North Korea following the border incident, which was the first shelling of civilian areas in South Korea since the 1950-53 war.

But US Defence Secretary Robert Gates will visit China next month, Mullen said.

Beijing has so far refused to join in worldwide condemnation of the North for the November 23 artillery attack, which killed four people including two civilians.

In Tokyo on Thursday, Mullen lashed out at China as he touted a united defence front with South Korea and Japan against North Korea.

"Northeast Asia is today more volatile than it has been in much of the last 50 years," the chairman of the Joint Chiefs said.

"Much of that volatility is owed to the reckless behaviour of the North Korean regime, enabled by their friends in China," Mullen said.

He also said he felt a "real sense of urgency" about building up three-way defence ties with Seoul and Tokyo. US forces have separately held major military drills with the two allies since North Korea's attack.

The admiral has proposed three-way drills and said that any threat is "much better addressed with all of us together, in terms of showing strength and getting to a point where we can deter North Korean behaviour".

That would also present a challenge for China, which has protested at US-led exercises being conducted near its territorial waters.

Foreign ministry spokeswoman Jiang Yu Thursday warned against any steps that "may lead to further escalation of tensions, gravely jeopardising peace and stability in the region".

Cai Jian, a professor at the Institute of International Studies at Fudan University in Shanghai, said Beijing was likely still exercising pressure behind the scenes on Pyongyang despite the unified stand taken by Kim and Dai.

"I don't know by what means this 'consensus' was reached. Persuasion or pressure? I can't guess that," he told AFP.

"But since China doesn't want to see the situation deteriorate, it must have made great efforts to try to bring North Korea back to the table."

But Choi Choon-Heum, analyst at Seoul-based Korea Institute for National Unification, said that for China "the biggest priority is aiding the North... so that it will remain as a buffer state against the US military presence in the Korean peninsula as long as possible.

"Pressuring Pyongyang to change its course at this point won't help achieve the goal, so I can't imagine Beijing putting real pressure on the North regarding the bombing on Yeonpyeong or its nuclear programmes."

The United States, meanwhile, opened up an unofficial channel of communication with New Mexico Governor Bill Richardson, a veteran North Korea troubleshooter, announcing a private visit to the North from December 16 to 20.

US State Department spokesman Philip Crowley said Richardson's planned visit was a private trip and that "he will not be carrying any particular message" from Washington.

In other shuttle diplomacy, Japan's pointman for the North Korean nuclear issue, Akitaka Saiki, headed for talks in Moscow with Russian Deputy Foreign Minister Alexei Borodavkin.

North Korea defended its artillery attack on the border island, saying the South's "puppet warmongers" had provoked the incident with its own naval drills.

South Korea -- whose capital Seoul is within artillery range of North Korea -- announced plans to supply additional gas masks to residents of its border islands in case of a chemical attack by the North.

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