Han's two-day visit will mark the 15th anniversary of the establishment of diplomatic relations.

Han was welcomed by Chinese Premier Wen Jiabao at the Great Hall of the People on Monday afternoon. His office said he was scheduled to meet President Hu Jintao on Tuesday.

Han "will explain the latest developments in inter-Korean relations, including the result of the recent inter-Korean prime ministerial talks, and ask for continued Chinese support for a peaceful settlement of the North Korean nuclear problem," an aide to Han told South Korea's Yonhap new agency.

The visit comes at a crucial time in multi-national efforts to scrap the North's nuclear programmes.

Last week US President George W. Bush sent a personal letter to the North's leader Kim Jong-Il, urging him fully to declare all nuclear activity.

The North carried out its first atomic test in October last year, sparking international concern.

But in February it reached a six-nation deal to disable its plutonium-producing plants and declare all nuclear programmes and facilities by year-end in return for major energy aid.

China chairs the six-nation talks which began in August 2003 and also include the two Koreas, the United States, Russia and Japan.

The US-supervised disablement of the main plutonium-producing facilities at North Korea's Yongbyon is going well.

However South Korean and US officials say the December 31 deadline for the declaration may be missed because of disagreements over the North's suspected highly enriched uranium weapons programme.