China reacted with customary caution to North Korea's shelling of a South Korean island

China is the one country with leverage over North Korea, keeping the regime from collapse with shipments of food and energy. Yet, as one of the worst crises on the Korean peninsula since the 1950-53 Korean War unfolds, China has avoided taking sides.

Beijing even risked appearing to implicitly brush off the incident, with its state-run Xinhua news agency announcing just hours after the deadly North Korean attack that a Chinese government delegation visiting North Korea had signed a new deal on economic and trade cooperation with its neighbor.

China has already antagonized many of its Asian neighbors -- particularly Japan -- by making more assertive territorial claims in the South and East China Seas in recent months.

The U.S. and many other Western countries are growing increasingly alarmed at China's more muscular diplomacy on a range of issues, including trade, climate change and human rights. China's unwillingness to go against North Korea, even as it escalates its military belligerence, is likely to further strain its relations in a region nervous about its strategic intentions.

Stephen Bosworth, special U.S. envoy for North Korea, arrived in Beijing for emergency talks Tuesday following the weekend's revelations about North Korea has dramatically expanded its nuclear program. The Chinese government also reserved judgement on the nuclear issue, calling only for a resumption of talks between North and South Korea, China, Russia, Japan and the U.S.

'China hopes that the relevant parties will do more to contribute to peace and stability in the region,' a spokesman for the Chinese Foreign Ministry, Hong Lei, told reporters.

'It is imperative now to resume the six-party talks.'

There was a suggestion of partiality, however, when the evening news broadcast on China's main state-controlled television channel gave greater prominence to North Korea's official version of events on the shelling, which blamed South Korea for firing at it first.

Shortly afterward, Xinhua announced that a delegation led by Chinese Deputy Commerce Minister Wang Hemin had signed the new economic and trade pact in Pyongyang at the sixth meeting of the DPRK-China Intergovernmental Committee for Cooperation in Economy, Trade, Science and Technology.

The Xinhua report gave no details of the pact, and didn't mention the day's violence.

Mr. Bosworth's mission in Beijing, following talks in Seoul and Tokyo over the last two days, is to persuade China to use its clout to curb North Korea's increasingly provocative behavior.

China's political influence in the North derives mainly from the Korean War, when it sent hundreds of thousands of 'volunteers' to fight U.S.-led United Nations forces. Today, it provides much of the North's food and electricity, and is its main trading partner and military backer.

Emerging from a meeting with Yang Jiechi, China's Foreign Minister, Mr. Bosworth said he had held 'useful' talks and the two sides had agreed that a multilateral approach was needed.

However, China is unlikely to comply with any request of greater pressure on the North, according to Yang Xiyu, a former Chinese diplomat who represented China in the six-party talks in 2004-2005.

'The U.S. hopes China will put more pressure, like sanctions, on North Korea. But from China's point of view the best way to persuade North Korea is not through sanctions, but dialogue,' he said. 'The main obstacle is not the question of whether pressure is enough, but how to reduce the strategic mutual distrust between the North and South, and between North Korea and the U.S.'

Mr Yang, now a senior fellow at the state-run China Institute of International Studies, said North Korea's recent actions had 'complicated' China's efforts to restart the six-party talks.

'But that only reveals the need for patience,' he added.

China has long tried to maintain the appearance of impartiality as host of the six-party talks, which it sees as a way enhance its reputation as a responsible member of the international community.

But those efforts are now being undermined by its openly cozy relations with a North Korean government that is pushing the limits of tolerance in the South, according to many foreign diplomats and analysts. They cited China's refusal to accept the results of an international investigation which blamed North Korea for the sinking of the Cheonan, a South Korean ship, in March, with the loss of 46 lives.

This time, however, China may struggle to prevent the U.N. Security Council from censuring North Korea, as the artillery raid occurred in broad daylight, and was shown live on television.

'This is moving a lot faster than the Cheonan incident, so I would expect this goes quickly to the U.N. so China doesn't have the time to use the usual delay and water-down techniques,' said John Delury, assistant professor at Yonsei University's Graduate School of International Studies. 'Chinese diplomats are going to be looking for ways to finesse this back to negotiation in the days to come, and that's going to be hard,' he said.

An ailing Kim Jong Il, North Korea's leader, made a surprise visit to China in August -- his second this year -- to meet President Hu Jintao, who took the rare step of travelling to northeastern China, near the North Korean border, for the meeting. It was a piece of diplomatic theater that underlined the fraternal relationship between the neighbors that was forged in war and is sustained by close links between the ruling parties.

There were rumors -- never confirmed -- that Mr Kim was accompanied in China by his third and youngest son, Kim Jong Eun, who was anointed as North Korea's next leader in September.

China's primary concern isn't to prevent North Korea from developing a nuclear weapon, but to ensure that the regime there doesn't suddenly collapse, sending a flood of refugees over the border into northeastern China.

There is also a common view among Chinese experts that a strong, unified Korea represents a threat to China as it would bring to its border a key U.S. ally, and the People's Liberation Army would end up face-to-face with thousands of U.S. troops stationed in the South.

'China can't be seen as an honest broker in this process,' said Nicholas Eberstadt, an expert on North Korea at the American Enterprise Institute in Washington.