WASHINGTON - US-China relationship needs direct involvement of top leaders to manage and Chinese President Hu Jintao's upcoming state visit provides a "good opportunity" to help restore positive momentum to the relationship, former US ambassador to China Stapleton Roy has said.

Roy, now director of the Washington-based Kissinger Institute on China and United States, made the remarks in a recent interview with Xinhua in the running-up to President Hu's visit scheduled for later this month. The ambassador, who was born in Nanjing, China, is one of the most respectable US experts on China-US relations.

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"The relationship between China and the United States over the past two years has continued to be a very rigorous one with engagement at all levels," the ambassador said when asked to give a general assessment of the relationship in the past two years since the Obama administration took office.

"The economic relationship has continued to be very active even though both countries were affected by the global downturn. Our exports to China declined less than our exports to other markets. And our imports from China have continued," he said.

Roy said the two countries have also been cooperating in other areas and on many issues, including very difficult issues such as the nuclear issues in Iran and on the Korean Peninsula.

Nevertheless, Roy said, the relationship has its downsides over the past two years. The military-to-military relationship, for example, is one of the areas in which the two countries have not been able to engage with each other effectively over the past two years, he said.

"There has also been friction in the relationship over the last two years, I would say, particularly over the last year, following the American arms sales to Taiwan and the president's meeting with the Dalai Lama," he said, referring to US arms sales to Taiwan and President Barack Obama's meeting with the Dalai Lama in the White House in the early months of 2010.

The ambassador said he believed that such friction had triggered nationalistic responses in both countries, causing strategic suspicions between the two sides.

"We do have an unhealthy level of mutual suspicions. And if we let this mutual suspicions grow, then we are going to damage the interests of both countries," Roy said.

"I think because of these factors, the visit by President Hu Jintao to the United States in January is so important," he said.

Roy said the joint statement issued by the two countries during President Obama's visit to China in November 2009 was "a very positive statement" which set numerous areas for bilateral cooperation and the goal of building a positive, cooperative and comprehensive relationship for the 21st century.

"I think the leaders still have those as that goal. But what we have seen from the attitude of each country could make it difficult to achieve that goal, which is why it is very important for the leaders to talk together," he said.

Asked how will President Hu's upcoming visit help promote bilateral ties, the ambassador highlighted the importance of direct contacts between top leaders of the two countries in handling such an important relationship.

"You can not manage relationship effectively between two big powerful countries like China and the United States if the top leaders are not directly involved and have contacts so they gain better understanding of each other," Roy said.

So the personal factor is very important, he said, although it is not the only factor because there are national interests that are larger than personality of the individual leaders.

Roy said that the top leaders of the two countries have continued the practice of frequent meetings started by former US President George W. Bush and President Hu, saying that such practice is "very desirable."

"Given the things I have talked about earlier, the mutual suspicions and the areas of our relationship that have not been developed fully, such as military-to-military contact, I think having President Hu come here provides a very good opportunity to see if we could restore positive momentum to the relationship in the spirit of the joint statement which was issued a year ago (in 2009) at the time of President Obama's visit," the ambassador said.

On the common interests of the two countries, Roy said he would like to look at the issue from the higher strategic level rather than the lower level of trivial issues. From a strategic level, the United States and China share common interests in a fair and just international system, he said.

"What country can be more positive in terms of trying to ensure there is a fair and just international system that operates under the condition of stability than the United States and China?" he asked.

"We can show by the pattern of cooperation between us that other countries will be able to operate in a world where cooperation between the two biggest economies and two of the most powerful countries is creating an international example of how countries have differences can still find sufficient common interests to have their relationship characterized by cooperation rather than conflict," the ambassador said.

"To me this is the challenge of the US-China relationship. To look at narrowly in terms of conflict-dominant relationship, it seems to me, is ignoring the possibility in the relationship and ignoring the national interests of both countries," he noted.

"How could China benefit from conflict with the United States and how could the United States benefit from conflict with China?" the ambassador asked.