MADRID (Reuters) -Delegations from the U.S. and China were set to continue their talks in Madrid into a second day on Monday over trade tensions and an imminent deadline for Chinese divestment from the short-video app TikTok.

The latest round of negotiations - the fourth in four months - took place at the baroque Palacio de Santa Cruz that houses Spain's foreign ministry and concluded its first day on Sunday after about six hours with no indication of a breakthrough.

Talks had centered on TikTok, tariffs and the economy, a U.S. government official said, offering no further details.

Delegations led by U.S. Treasury Secretary Scott Bessent and Chinese Vice Premier He Lifeng have been meeting in European cities since May to try to resolve differences that prompted President Donald Trump to raise tariffs on Chinese imports and sparked tit-for-tat measures, including China imposing similarly high import duties for U.S. goods and halting the flow of rare earths to the U.S.

The delegations last met in Stockholm in July, where they agreed to extend for 90 days a trade truce that sharply reduced triple-digit retaliatory tariffs on both sides and restarted the rare-earth exports from China to the United States.

Experts had low expectations of a significant breakthrough in Madrid, with the most likely result seen as a further extension of a deadline for TikTok's Chinese owner, ByteDance, to divest its U.S. operations by September 17 or face a U.S. shutdown.

"I'm not expecting anything substantive between the U.S. and China unless and until there is a one-on-one meeting between Trump and Xi. Setting that up is really what these talks are all about," said William Reinsch, a senior trade adviser at the Center for Strategic and International Studies, a Washington think tank.

Trump has repeatedly expressed interest in a meeting with Xi, but Reinsch said that the Chinese would not agree to a Trump-Xi meeting until they know the outcome and are pushing for further easing of U.S. export controls on chips and other high-tech goods.

"This meeting is an opportunity to measure each other's positions and to learn more about each side's red lines," Reinsch said.

China's embassy in Madrid notified reporters of a potential concluding news conference on Monday afternoon, indicating that the talks could wrap up quickly. Some previous discussions over more complicated issues, such as talks in London over rare earths shipments, extended to a third day.

Bessent was scheduled to be in London on Tuesday to meet with British Finance Minister Rachel Reeves ahead of Trump's state visit with King Charles that starts on Wednesday.