US President Donald Trump changed tack and agreed to honour the "one China" policy during a phone call with China's leader Xi Jinping, a major diplomatic boost for Beijing which brooks no criticism of its claim to self-ruled Taiwan.
Trump angered Beijing in December by talking to the president of Taiwan and saying the United States did not have to stick to the policy, under which Washington acknowledges the Chinese position that there is only one China and Taiwan is part of it.
A White House statement said Trump and Chinese President Xi had a lengthy phone conversation on Thursday night, Washington time.
"President Trump agreed, at the request of President Xi, to honour our 'one China' policy," the statement said.
Reaction from Taiwan was muted. A spokesman for President Tsai Ing-wen said in a statement it was in Taiwan's interest to maintain good relations with the United States and China.
The US and Chinese leaders had not spoken by telephone since Trump took office on January 20.
No issue is more sensitive to Beijing than Taiwan. China and the United States also signalled that with the "one China" issue resolved, they could have more normal relations.
"Representatives of the United States and China will engage in discussions and negotiations on various issues of mutual interest," the statement said.
In a separate statement carried by China's Foreign Ministry, Xi said China appreciated Trump's upholding of the "one China" policy.
"I believe that the United States and China are cooperative partners, and through joint efforts we can push bilateral relations to a historic new high," the statement quoted Xi as saying.
"The development of China and the United States absolutely can complement each other and advance together. Both sides absolutely can become very good cooperative partners," Xi said.
Taiwan's presidential office spokesman Alex Huang said in a statement that the island's government and the United States "both maintain close contact and communication so as to keep a 'zero accident' approach" to their relationship.
In Beijing, Chinese Foreign Ministry spokesman Lu Kang said the "one China" principle was the political basis of Sino-US ties.
"Ensuring this political basis does not waver is vital for the healthy, stable development of China-US relations," Lu said.