Chinese President Hu Jintao and US counterpart George W. Bush exchanged congratulations Thursday on the 30th anniversary of diplomatic ties and vowed even closer relations, state media reported.

Hu's message called the establishment of formal diplomatic ties on January 1, 1979, a key moment in world history and said China was eager to work with the United States in facing today's global challenges.

"In a time of deep and complex world change, China is willing to join with the United States in facing new opportunities and challenges," Hu said, according to the state-run Xinhua news agency.

Xinhua quoted Bush as saying in his message that China and the United States had in the past 30 years "transcended deep cultural and political differences, bridging a wide gulf."

Bush also called for greater bilateral cooperation, it said.

The messages came as Xinhua ran a separate commentary noting improving ties and calling for the two sides to join forces in addressing the global economic crisis.

The United States switched its diplomatic recognition to communist-ruled China 30 years ago, ending decades of close support for the Nationalist Chinese government of Taiwan.

The Nationalists had fled to Taiwan from mainland China in 1949 after losing a civil war.

"Thirty years ago China and the United States established diplomatic relations, a significant milestone in the two countries' history that opened a new page in relations and left a far-reaching impact on the world situation," Hu's message to Bush said.

Hu also called for both sides to increase cooperation in trade and other areas.

Ties have improved dramatically from their Cold War nadir, especially in trade, with the two sides increasingly dependent on each other economically.

Yet numerous sore points remain, including continued US military help for Taiwan, recurring disputes over trade practices, China's human rights record, and American suspicions over Beijing's military modernisation.

The Xinhua commentary noted relations had not always been smooth and urged both sides to "really cherish" recent developments in relations."

Neither of the reports made mention of what China expected from US president-elect Barack Obama.

At the height of presidential campaigning last year, Obama accused China of manipulating its currency and called for Beijing to change its foreign exchange policies to rely less on exports and more on domestic demand for growth.

The yuan's value has been one of the particularly sensitive issues between China and the United States, which has accused Beijing of deliberately keeping its currency low to protect the competitiveness of Chinese export prices.