"As host of the six-party talks on the nuclear issue on the Korean Peninsula, China has played a crucial role on this pressing issue," Annan told students at Beijing University.

China's ongoing leadership would be essential to ensure that multilateral diplomatic efforts result in a nuclear weapons free Korean Peninsula, he said.

"We cannot allow the current stalemate to continue. All parties will need to redouble their efforts," Annan said.

He made a speech to about 200 students and teachers in China's prestigious Beijing University on Tuesday morning.

Annan spoke highly of China's role in international affairs including preventing the spread of HIV/AIDS and reducing poverty.

He encouraged students of Beijing University to join in international efforts in protecting the global environment. Annan suggested Chinese students enhance exchanges with young people in Japan and the Republic of Korea (ROK), and do their bit to protect the environment such as planting trees.

Before arriving in China, Annan visited the ROK and Japan. He suggested the three Asian countries improve relations by working together in areas such as environmental protection.

Annan concluded his five-day official China visit on Tuesday afternoon. He left for Vietnam to continue his Asian tour.