Talks restarted at Spain's foreign ministry, a day after delegations led by US Treasury Secretary Scott Bessent and Chinese Vice Premier He Lifeng opened the latest round of discussions. The meetings are expected to continue through Wednesday.

Officials from the two nations were seen entering the headquarters of the ministry on Monday morning, according to an AFP reporter at the scene.

The agenda includes two of the thorniest issues in the bilateral relationship: President Donald Trump's threat of steep tariffs on Chinese imports and Washington's demand that TikTok be sold to a non-Chinese owner or face a US ban by September 17.

Trade tensions escalated sharply earlier this year, with tit-for-tat tariffs reaching triple digits and snarling supply chains.

Both governments later agreed to roll back duties to 30 percent on US goods and 10 percent on Chinese exports, but the temporary truce expires in November.

Beijing urged Washington last week to resolve disputes "on the basis of mutual respect and equal consultations."

Over the weekend, China launched investigations into the US semiconductor sector, signalling frictions remain high despite the Madrid talks.

The meetings could lay groundwork for a possible summit between Trump and Chinese leader Xi Jinping later this year.

Until then, negotiators face the challenge of stabilising an uneasy truce while addressing disputes over technology access, tariffs and rare earth exports.