Beijing, China - China on Thursday called on the US to "refrain from intervening" in self-ruled Taiwan's elections, slamming official visits between the island and the US after Washington said it would send a delegation there following this week's crucial polls.

Washington must "refrain from intervening in the elections in the Taiwan region in any form, so as to avoid causing serious damage to China-US relations", foreign ministry spokesperson Mao Ning said.

"China always firmly opposes any form of official exchanges between the US and Taiwan," she added, following Washington's announcing plans to send an "unofficial" delegation to Taiwan after a crucial election on the self-ruled island.

"There is only one China in the world, and Taiwan is an inalienable part of China," she added.

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Mao also condemned a US warning to Beijing against stoking tensions over the polls.

China "expresses strong dissatisfaction and resolute opposition to the American side's brazen chattering about the elections in the Taiwan region," she said.

"Taiwan is the core of China's core interests and is the number one red line that must not be transgressed in the China-US relationship," Mao stressed.

"We urge the US side... to take practical actions to deliver on the commitments made by the two countries' leaders," she said.

The move to send a US delegation to Taiwan comes amid rising tensions over Saturday's presidential and parliamentary elections. China has previously reacted angrily to official visits, such as the one made by then-House Speaker Nancy Pelosi in 2022.