BEIJING/SEOUL North Korean leader Kim Jong-il won a warm embrace from China on a visit this week that prompted an icy response from other regional powers who had hoped Beijing would help tame the isolated state.
Kim's rare trip abroad, by train because of his terror of flying, came as the North slides deeper into economic trouble from U.N. sanctions for last year's nuclear test.
It also came amid rising diplomatic tension between Seoul and Beijing over North Korea's role in the sinking of a South Korean navy ship.
China's Xinhua news agency said Kim was given a warm welcome by President Hu Jintao, making no reference to the ship, which officials in the South believe North Korea sank with a torpedo in late March.
Witnesses at the Chinese border city of Dandong said Kim's armored train crossed the border back into North Korea on Friday afternoon.
Xinhua quoted the North Korean leader as repeating a commitment to end the nuclear arms program, that is seen as a major risk to economically powerfully North Asia, and his willingness to discuss returning to international disarmament talks which he has boycotted for 1-½ years.
"The North Korea side stated that its stance in favor of denuclearization of the Korean Peninsula has not changed," Xinhua said. "The North Korean side is willing, together with all parties, to discuss creating favorable conditions for restarting the six-party talks."
North Korea's KCNA news agency relayed a message of thanks from Kim to Hu which praised the "world-startling achievements" made by China "after doing away with the centuries-old backwardness". No mention was made of the nuclear stand-off or other substantive issues.
South Korea has expressed its displeasure that China had rolled out the red carpet so soon after the sinking of one of its warships near their disputed border.
South Korean President Lee Myung-bak said he believed his giant neighbor would come round once investigators reach a final conclusion, which is expected later this month.
"The Chinese government will understand and play a role," Lee was quoted as telling ruling party officials.
But many analysts say China is so concerned about North Korea's stability that it is prepared to bankroll Kim even if it does put it at odds with others in the region.
"China is paying more attention to North Korea's stability, needing to avoid chaos on the Korean peninsula," said Zhang Liangui, an expert on North Korea at the Central Party School, a prominent institute in Beijing.
"If you neglect that problem, North Korea may suffer turmoil. China does not want the North Korean system to see that kind of trouble."
Seoul is not convinced.
"It (China) is looking at short-term stability, not long-term," complained one senior South Korean official whose government has said it will push hard for the North to be punished if it turns out to have sunk the ship.
The issue is likely to dominate a series of talks this month between China, Japan and South Korea, first among foreign ministers and then their leaders.
Investigators have found traces of gunpowder and metal pieces from the sunken ship that are consistent with a torpedo, possibly a German made one picked by the North to avoid implicating itself, a senior South Korean official was quoted as saying by Yonhap news agency.
North Korea has denied involvement and accused Lee of trying to use the incident for political gains ahead of local elections in June.
Xinhua quoted Kim as saying that he welcomed Chinese investment in his country "based on the principles of mutual benefit and win-win".
Some analysts have said there is a degree of resentment in the North that its economy is increasingly dominated by China but it has little choice as South Korea, once a major benefactor, has ended aid over the nuclear issue.
Kim, seen by media in China looking haggard and with thinning hair and a limp, was taking his first trip abroad since a suspected stroke in 2008 in a visit seen as focused on winning economic aid.
Kim's last visit to China in 2006 brought effusive promises of economic cooperation between the two neighbors, and vows from the North Korean leader to seek progress toward denuclearization. But both goals have sputtered.
(Additional reporting by Emma Graham-Harrison and Lucy Hornby in Beijing and Jonathan Thatcher in Seoul; Editing by Nick Macfie)