President Hu Jintao and Premier Wen Jiabao congratulated US President Barack Obama on his re-election on Wednesday, noting the "positive" achievements in relations during the past four years.

In his message of congratulations, Hu said China will "look to the future and continue to strive for greater progress in the China-US partnership," Foreign Ministry spokesman Hong Lei said at a daily briefing shortly after Obama's re-election.

Vice-President Xi Jinping also sent a message of congratulations to US Vice-President Joe Biden, Hong said.

The election means Washington will engage more with Beijing during Obama's final term, experts said.

They generally hold an optimistic outlook for China-US relations.

A number of experts said one of Obama's main challenges over the next four years will concern fleshing out US policy. This includes military "rebalancing" in the Asia-Pacific region. He also has to put in place a new foreign policy team and formulate durable trade policies with China.

Cai Mingzhao, spokesman for the 18th National Congress of the Communist Party of China, said on Wednesday China expects the US to "respect each other's core interests" and "effectively manage and control" friction.

A number of China specialists in the US have approved of Obama's China approach so far, especially regular exchanges in trade, defense, culture, education and tourism.

China and the US are each other's second-biggest trading partners. In 2011, Chinese imports of US goods and services exceeded $100 billion for the first time, making China the fastest-growing US export market, according to the Ministry of Commerce.

In addition to the thousands of US investments in China, the US has become a popular investment destination for Chinese companies.

The world's two biggest economic powers have worked to address pressing global and regional issues such as the financial crisis, climate change and nuclear security.

Despite pressure from Congress, the Obama administration has not labeled China a "currency manipulator".

Michele Flournoy, senior foreign-policy adviser to the Obama re-election campaign and a former undersecretary of defense for policy, told China Daily earlier that she didn't foresee any second-term changes by Obama toward China.

"President Obama will continue to invest in this relationship, which is so critical to both of us economically and to stability across the region," she said.

Bai Fengjun, research director at the United States Information Technology Office in Beijing, is optimistic.

"It's easier for China to deal with an existing administration and Democrat policies are better toward China, not as tough as the Republicans," Bai told China Daily.

But ties will face challenges, Bai said.

One of these challenges, according to Jonathan Pollack, an expert on Asia-Pacific security at the Brookings Institution and acting director of its John L. Thornton China Center, is to find suitable replacements for his departing foreign-policy team, led by Secretary of State Hillary Clinton and Kurt Campbell, assistant secretary for East Asian and Pacific affairs.

Senator John Kerry is tipped to succeed Clinton. The Massachusetts Democrat, who lost his bid for the presidency against George W. Bush in 2004, has ample experience in foreign policy.

Also on the shortlist are US Ambassador to the United Nations Susan Rice and Tom Donilon, Obama's national security adviser.

Da Wei, an expert on US studies with the China Institutes of Contemporary International Relations, said building trust as new people take up positions will be a priority.

"As the US aims to increase engagement with countries in this region, it should not be at the cost of its relationship with China,'' Da said.

Douglas Paal, director of the Asia program at the Carnegie Endowment for International Peace, said Obama should change his Asia policy by focusing more on the economy.

The president of the US-China Business Council, John Frisbie, said earlier that the US should focus on better interaction with China.

Such an approach has led to the yuan appreciating by more than 30 percent since 2005, Frisbie added.

A survey by the council showed more than 90 percent of US firms that have invested in China have done so mainly to serve the Chinese market, not to outsource production and export back to the US.

Wang Honggang, assistant director of the Institute of American Studies at the China Institutes of Contemporary International Relations, said that during Obama's second term there will probably be fewer tensions as both countries have experience in dealing with each other.

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