The United States on Wednesday "forcefully" pressed China on festering maritime rows and human rights, even as the two countries vowed to seek cooperation rather than confrontation.

Opening two days of talks between the world's two largest economic powers, US Secretary of State John Kerry warned his Chinese counterparts that it would be "unacceptable" to try to create a new status quo in the South and East China Seas, where Beijing is in dispute with its neighbours.

He also did not "pull any punches" when it came to human rights issues, highlighting Washington's "perception of a trend in China with an increase in arrests, with an increase of harassments, of individuals who are expressing political views," a senior US administration official said.

Chinese President Xi Jinping earlier sought to brush aside disputes, saying it was "natural that China and the US may have different views and even frictions on certain issues".

"This is what makes communication and cooperation even more necessary," he urged.

"If we are in confrontation it will surely spell disaster for both countries and for the world," he said, adding the Pacific powers needed to "break the old pattern of inevitable confrontation".

But in a small circle of top leaders at the sixth annual Strategic and Economic Dialogue, Kerry raised some of the thorniest issues bedevilling US-China ties, telling State Councillor Yang Jiechi that nations cannot "be permitted simply to act unilaterally to advance territorial claims or interests".

"We believe that a rules-based order in the Asia-Pacific region is essential," the senior US administration official said, adding "we want China to contribute to and participate in that order, not pull against regional and global norms".

"Trying to fix the problem through creating a new status quo at the expense of regional stability and regional harmony is unacceptable," the US official added.

China lays claim to almost all of the strategic South China Sea -- also claimed in part by the Philippines and Vietnam, among others.

In recent months, China has more aggressively pursued its territorial ambitions, triggering rising tensions with boats ramming each other, the use of water cannon and arrests of fishermen.

China is also embroiled in a row with US security ally Japan over Tokyo-controlled islands in the East China Sea, with both Asian powers regularly sending patrol ships and aircraft to the area.

- Talking tough -

Kerry, who with Treasury Secretary Jacob Lew is leading a large US delegation to the talks, urged China to avail itself of international mechanisms to resolve the competing claims.

The top US diplomat also renewed pleas to Beijing to ensure respect of cultural, religious and ethnic rights across its regions including Tibet and far western Xinjiang, home to the mostly Muslim Uighur minority, which has seen a spate of violent incidents.

"I would wager that no one on the Chinese side of the table... today thought that Secretary Kerry was going easy on human rights," the US administration official said, adding Kerry "didn't pull his punches".

Outspoken Tibetan writer Tsering Woeser told AFP she was being held under house arrest during the dialogue, after US diplomats invited her to meet visiting officials.

Several police officers were stationed outside her apartment in Beijing, she said, adding: "It's to stop me from going to the US embassy."

Climate change was also a top focus, as the two largest emitters of the greenhouse gases that cause global warming agreed to launch eight pilot projects aimed at reducing their carbon footprints.

"People around the world are demanding action," Kerry told a working group on the issue.

"Climate change respects no borders, no boundaries, and affects the entire planet. For better or worse, we are now aware of the consequences of inaction in ways that we never have before."

US special envoy for climate change Todd Stern said the two sides had had some "constructive" talks ahead of a UN meeting due in Paris next year to set new global gas emissions targets for after 2020.

"It is crucial for China to play a very important role in reducing emissions," Stern said.

Xie Zhenhua, vice chairman of the National Development and Reform Commission, told reporters Beijing was working on setting its targets.

"In terms of responding to climate change we share common but differentiated responsibilities," Xie stressed.

China has long argued that it remains a developing country despite its economic clout, and as such should not have to shoulder the same burden for reducing greenhouse gases.