Chinese President Hu Jintao congratulated North Korean leader Kim Jong-il on his re-election as head of the country's ruling party at a rare conference, but made no direct mention of Kim's son and probable successor.
"I hereby extend my warm congratulation on the successful holding of the conference of the WPK, on your re-election as general secretary of the WPK, and on the re-election and formation of a new highest leading body of the WPK," state news agency Xinhua quoted Hu as saying in his message.
WPK stands for the Workers' Party of Korea.
Hu said China would "always handle, maintain and boost China-DPRK relations from a strategic height and a long-term perspective ... despite the ups and downs of the international situation", Xinhua reported, referring to the North's formal name.
"We are willing to make joint efforts with the DPRK to continuously promote China-DPRK relations to a higher level, in order to better benefit the two peoples and make greater contributions to realising lasting peace and common prosperity in the region," Hu added.
"I sincerely wish General Secretary Kim and the WPK to keep making new and greater achievements in the cause of leading the DPRK people building a strong and prosperous country," he said.
China is the North's only real ally, though ties have been considerably strained by Pyongyang's nuclear programme.
Kim visited China last month, possibly with his son, in what analysts said was a trip partly to brief Beijing on the succession plan.
His son, Jong-un, became his second-in-command on the ruling Workers' Party's powerful Central Military Commission on Wednesday, positioning him up for succeed his 68-year-old father, whose health is reported to be worsening after a 2008 stroke. (Reporting by Ben Blanchard; Editing by Alex Richardson)