The presidents of China and South Korea on Tuesday agreed to develop a strategic partnership and promised more cooperation on regional issues such as North Korea, reported dpa.
Chinese President Hu Jintao and his South Korean counterpart, Lee Myung Bak, agreed to upgrade bilateral relations to a "strategic cooperative partnership," state television said.
Hu said the two sides should expand trade and investment ties, and become more involved in multilateral cooperation on security in North-east Asia, UN reform and climate change.
China would "continue to play a constructive role" in six-party negotiations on ending North Korea's nuclear weapons programme, Hu was quoted as saying.
"China is willing to work with other parties to comprehensively implement the second phase of the six-party talks," he said.
South Korea would also continue working to resolve the nuclear negotiations and saw "some achievements" from the earlier rounds, China Central Television quoted Lee as saying.
Foreign ministry spokesman Qin Gang earlier said Wu Dawei, China's chief negotiator, would meet his US, North Korean, Japanese and South Korean counterparts in the next few days.
US Assistant Secretary of State Christopher Hill and North Korean Vice Foreign Minister Kim Kye Gwan were in Beijing for the talks, state media said.
The latest obstacle stalling the negotiations is North Korea's failure to give a full declaration of all nuclear programmes and facilities, which it had agreed to do with the other five nations involved in the talks.
North and South Korea, the United States, China, Japan and Russia last held talks in October.
Hu also thanked Lee for sending a South Korean rescue team to China's earthquake-devastated province of Sichuan and said donations for relief work from South Korean citizens "fully reflect the deep friendship between our two countries".
He accepted an invitation to visit South Korea in the second half of this year, while Lee agreed to attend the opening ceremony of the Beijing Olympics in August.
Lee said the Olympics would have "deep significance" and backed Hu's leadership of earthquake relief in Sichuan, where at least 67,000 people died.
"I hope, under the leadership of President Hu Jintao, Chinese people can work together and rebuild their homes as soon as possible," the semi-official China News Service quoted Lee as saying.
The two sides signed several agreements covering fields including science and technology, justice and education, the agency said.
Qin said China believed the military alliance between the United States and South Korea was a "Cold War product".
He said said East Asian nations had "also changed a lot" since the US-South Korean alliance was forged in the 1950-53 Korean War.
Lee's four-day visit is his first trip to China as South Korea's leader. He is also scheduled to visit the eastern port of Qingdao, which is home to about 5,000 South Korean companies.