China and the United States should work hard to cultivate a "mutual circle of friends" instead of exclusive cliques, said Chinese President Xi Jinping, in a call aimed at calming tensions over the South China Sea.

"China and the US have extensive mutual interests in the Asia-Pacific region," he said at the opening of the annual US-China Strategic and Economic Dialogue (S&ED).

"We should hold regular dialogues, cooperate, cope with various challenges, work hard to cultivate a mutual - not exclusive - circle of friends, and become the builders and protectors of regional prosperity and stability."

Mr Xi also called for regular contact between both sides to build mutual trust and to avoid strategic misjudgment, as he stressed the need to avoid adopting a confrontational attitude towards any differences, which are to be expected in the Sino-US relationship.

Similarly, US President Barack Obama said - in remarks delivered on his behalf at the opening ceremony - that it was hard for both nations to agree on all issues due to their unique histories and traditions.

"But we must continue to build a bilateral relationship based on shared interest, responsibility and challenges, and jointly undertake the duty of strengthening the international order," added Mr Obama.

The two-day S&ED - the premier platform for Sino-US dialogue and cooperation since 2009 - is co-chaired by US Secretary of State John Kerry and Treasury Secretary Jacob Lew, as well as Chinese State Councillor Yang Jiechi and Vice-Premier Wang Yang, who oversee foreign policy and trade respectively.

This year, the dialogue is taking place amid heightened tensions in bilateral ties concerning the South China Sea, where there are overlapping territorial claims by China, Taiwan and several Asean nations.

The US has conducted freedom of navigation operations in the maritime hub in response to military deployment and infrastructure construction on reclaimed islands by China.

At the IISS Shangri-La Dialogue last weekend in Singapore, US Defence Secretary Ashton Carter warned Beijing it was erecting a "Great Wall of self-isolation" through its assertive actions, while Chinese Admiral Sun Jianguo accused Washington of destabilising the region with its military presence.

Analysts say Mr Xi's call for developing mutual friends between Beijing and Washington - a first by the Chinese leader - reveals China's concern that a split in international opinion over the South China Sea disputes might signal a return to the Cold War era where the US and the then Soviet Union maintained exclusive cliques.

Sino-Asean issues expert Xu Liping of the Chinese Academy of Social Sciences said there are worrying signs, with China and the US lobbying for support from other countries for their stances and actions over the South China Sea.

"Xi is warning against this development because a Cold War-like scenario would hurt global stability and, in turn, China's development," he told The Straits Times.

Citing South Korea and Singapore as positive examples of mutual friends who enjoy a healthy relationship with both China and the US, analysts say Mr Xi's call is an achievable prospect. "The key is to view any disputes as temporary problems and to take a longer-term view of the relationship," Peking University's Sino-US relations expert Niu Jun told The Straits Times.

Despite differences over the South China Sea, China and the US yesterday cited how they have worked together on issues such as North Korea and climate change.

Topping the agenda this year is the proposed Bilateral Investment Treaty, which is targeted for conclusion before Mr Obama leaves office next January. Other issues include the pace of China's economic reforms, with Mr Lew yesterday criticising China for its excess steel production and its "distorting and damaging effect" on global markets.

"Implementing policies to substantially reduce production in a range of sectors suffering from overcapacity, including steel and aluminium, is critical to the function and stability of international markets," he added.