For Zhou Wenzhong, who has spent almost three decades as a career diplomat focused on Sino-US relations, the two countries have never before shared so many common interests.

"Mutual beneficial cooperation has never been so extensive," said the Chinese ambassador to the United States on Friday, nine days before US President Barack Obama embarks on his first trip to China.

Zhou, 64, said the Sino-US relationship has developed into be one of the most important and dynamic bilateral relationships in the world. "Its strategic significance and global influence have been increasing day by day," Zhou said.

Those ties have maintained a positive momentum this year, with an abundance of meetings between representatives of the two countries.

"Such frequent high-level visits in the first year of a US administration are extraordinary in bilateral history," said Zhou, whose first posting was as secretary in the Chinese mission in Washington in 1978, a year before the nations forged diplomatic ties.

"High-level exchange plays an irreplaceable role in building trust and cooperation and propelling bilateral ties forward," he said.

"The first meeting (between President Hu Jintao and Obama) in April was extremely important in charting the roads for bilateral ties."

The two leaders then agreed to build a bilateral relationship characterized by cooperation.

Obama called Sino-US relations as "important as any bilateral relationship in the world", and expressed a desire for a more active and constructive relationship.

Zhou spoke highly of Obama's 4-day visit to China which starts on Sunday. According to Zhou, the two leaders will exchange views on issues affecting not only the their own countries, but also ones of regional and global significance.

"China and the United States shoulder important responsibilities and share a broad common interest in a host of vital issues relating to the peace and development of humankind," he said. The economic recession, climate change, energy and natural resources, public health, and the nuclear ambitions of Pyongyang and Teheran are among those concerns.

The Chinese ambassador, who once also served as deputy consul-general in San Francisco and consul-general in Los Angeles, and as minister in the embassy in the 1980s and '90s, did not shy from discussing the differences between the two countries.

"With different political systems and ideologies, it is natural for the two countries to have differences. The key is to establish a mechanism to address issues through dialogue and cooperation," Zhou said.

Zhou has witnessed a bilateral tie that has evolved from one of frequent tensions to one of extensive cooperation.

"Taiwan is the most important and most sensitive core issue in Sino-US relations. And we hope the US will adhere to its commitment, prudently handle issues relating to Taiwan and act to support the peaceful development of Cross-Straits relations," said Zhou, who assumed his current post in 2005 as the eighth Chinese ambassador to the US.

Zhou also reiterated China's sovereignty over the Tibet and Xinjiang Uygur autonomous regions.

"The US government has repeatedly expressed its respect for China's sovereignty and territorial integrity, acknowledged Tibet and Xinjiang as part of China and the US will not support Tibet independence and other activities aimed at separating Xinjiang from China," he said. "We hope the US side will keep its promise with actions and won't provide support and convenience to anti-China separatist forces."

On the environment, Zhou said China and the US, as the largest developing nation and the largest developed nation, have a broad common interest in fighting climate change and strengthening energy security.

Meanwhile, China and the US should continue stimulus measures to facilitate the economic recovery and growth of their economies, Zhou said.

While acknowledging the US concern for the rising unemployment and other problems caused by the global recession, Zhou said China opposes protectionism in trade and investment and advocates dialogue to solve trade friction.

He called on the US to recognize China's full market economy status and relax its restrictions on hi-tech exports to China.