The one-China policy, which has been challenged by US president-elect Donald Trump, is supported by the Democratic and Republican parties, US Secretary of State John Kerry assured Chinese Foreign Minister Wang Yi on Thursday.

Analysts said that through the phone call, Kerry aimed to warn Trump, who will be sworn in on Jan 20, not to undermine the cornerstone of Sino-US relations as the president-elect has done in the past month — from speaking with Taiwan leader Tsai Ing-wen on the phone to questioning the necessity of supporting the one-China policy.

Support for the one-China policy is based on the three joint communiques between the United States and China, Kerry said in his call to Wang. The communiques, issued in the 1970s and 1980s, laid the foundation for the restoration of China-US diplomatic ties.

Wang, noting that the Sino-US relationship is in a transition period, replied that the two sides should make joint efforts to keep bilateral ties going in the right direction.

Ruan Zongze, vice-president of the China Institute of International Studies, said that as a veteran diplomat, Kerry is "quite clear about how serious the consequences would be" if the one-China policy is challenged by a US president, and that's why he made the phone call.

He said the phone call also could be seen as a warning to Taiwan leader Tsai Ing-wen, who made a congratulatory phone call to Trump on Dec 2. The call broke four decades of Sino-US diplomatic precedent.

Tsai will transfer in Houston and San Francisco on her way to and from Latin America in a trip that will begin on Saturday. It was not clear whether she planned to meet with anyone in the US.

Wang Hailiang, a researcher of Taiwan studies at the Shanghai Academy of Social Sciences, said that challenging the one-China policy would not benefit the US, since China would take countermeasures to safeguard national sovereignty.

"The Sino-US relationship has always experienced turbulence at US power transitional periods in past decades, but it finally goes onto the right track," he said.