Kurt Campbell, the former US assistant secretary of state for East Asian and Pacific Affairs, called on Tuesday for China and the US to work together more.

Campbell said while he would love to see progress on thorny issues such as cyber security during the upcoming state visit by Chinese President Xi Jinping, what is missing in the US-China relationship is some visionary mission that the two countries can actually work together on.

He cited the example that during the height of the Cold War, the US and the Soviet Union still kept a robust space cooperation program.

"I don't think we are able to go to Mars alone. I don't think China can. But I think maybe together that's something we can contemplate, we can think about," said Campbell, who left the Obama administration in February 2013 and is now chairman and CEO of the Asia Group.

He believes that beyond something like climate change, the two countries have to find something that animates a spirit of cooperation, including cyber security and South China Sea.

Many observers believe that the two countries need to do a better job of expanding cooperation while effectively managing their differences.

Campbell said it's not appropriate for anyone to talk about checking Chinese power in Asia. "I think what I try to talk a lot about is how to advance American purpose and engagement across Asia," said Campbell, regarded as one of the masterminds of US rebalance to Asia strategy.

Reflecting on President Xi's comments that the Pacific Ocean is big enough for China and the US, Campbell said Asia and the Pacific are certainly big enough for the two countries to coexist. "I believe coexistence is not only inevitable but necessary," he said.

Campbell said he is ultimately hopeful on US-China relations, but said a level of anxiety and contention in the relationship is here to stay.

"We need to learn to work with that in the large context, as opposed to trying to go back to some period in time, in which the US-China relations were less tense, and less difficult. That period, I am afraid, is over."

He said understanding that clearly and recognizing that, but still understanding the importance of US-China relations is the "essential wisdom of what we need to accomplish."

John Hamre, president and CEO of the Center for Strategic and International Studies, said he believes that China understands that it cannot exclude the US and the US understands that it cannot contain China. But he said the two countries are yet to figure out how to work together and not to exclude other countries in the region.