South Korean media say North Korean leader Kim Jong Il may have begun a visit to his neighbor and ally, China. The reports quote South Korean officials as saying intelligence on Wednesday showed a special train crossed the border from North Korea into China - possibly carrying Kim and his entourage. The visit would come as China works to repair relations damaged by the North's recent missile tests.

Chinese officials have publicly expressed frustration with North Korea after the reclusive Stalinist nation last month test-fired seven missiles into the Pacific Ocean. Pyongyang's relations with China and other nations have been further strained following reports this month that the North may be preparing to test a nuclear weapon.

Kim Jong Il (file photo)

Analysts say China probably invited Kim Jong Il in hopes of convincing him not to go ahead with such a test. Andrei Lankov is a professor at the Australian National University's China and Korea Centre.

"From what we know, it seems the Chinese are seriously annoyed by the North Koreans' activities," he said, "and they are sending signals to Pyongyang that something should be done about Pyongyang's policy, and that especially, the recent missile launch was not a good idea at all."

Before the July missile launches, Beijing appeared to be cautioning the North Koreans against carrying out the tests, and afterwards, there were open signs of Chinese frustration.

In a recent interview with a South Korean newspaper, a senior official Chinese Foreign Ministry official said that "North Korea does not listen to China," despite what he said is a continuing friendship between the two Communist neighbors.

All signs are that Beijing hopes to use what remains of that friendship, and the influence it exerts as the chief supplier of food and fuel to the North, to convince Kim to stop the provocative acts.

Professor Lankov says concern is growing among the Chinese leadership that Pyongyang's actions may lead to a collapse of the regime and a reunification with South Korea - something Beijing desperately wants to avoid.

"They don't want North Korea to collapse, or to put it simply, they don't want a democratic revolution to happen in North Korea, because it might bring unification of Korea, and a unified Korea would probably be an ally of the United States," he said.

Lankov and other analysts say China will likely be pushing for North Korea to return to six-nation negotiations on ending its nuclear program. Pyongyang has boycotted the talks after the United States imposed sanctions on the country last year over its alleged counterfeiting and money laundering activities.

Chinese officials neither confirmed nor denied reports of a secret visit by Kim Jong Il, but in an unusual departure, the official China Daily newspaper ran a wire service article last week predicting that Kim would be coming. In the past, the Chinese have refrained from confirming Kim's visits until after his departure.