AFP journalists saw officials from both sides, led respectively by Chinese Vice Premier He Lifeng and US Treasury Secretary Scott Bessent, enter the Swedish government building serving as the talks venue.

Neither side has so far made public any information about what has gone on in the talks, which started on Monday.

The negotiations are happening in the wake of a US-EU trade deal struck over the weekend that set US tariffs on most EU imports at 15 percent, but none on US goods going to the EU.

The truce between China and the United States, the countries with the worlds two top economies, has temporarily set US duties on Chinese goods at 30 percent, and Chinese levies on US ones at 10 percent.

That accord, reached in Geneva in May, brought down triple-digit tariffs each side had levelled at the other after a trade war sparked by US President Donald Trump spiralled into a tit-for-tat bilateral escalation.

The 90-day truce is meant to end on August 12. But there are indications both delegations want to use the Stockholm talks to push the date back further.

The South China Morning Post, citing sources on both sides, reported on Sunday that Washington and Beijing are expected to extend their tariff pause by a further 90 days.

- Trump's threats -

Trump has threatened to hit dozens of other countries with stiffer tariffs from Friday this week unless they agree to trade deals with Washington.

Among them are Brazil and India, which he has warned could be targeted for 50-percent tariffs.

The US leader has already announced deal outlines with five countries -- Britain, Vietnam, Japan, Indonesia and the Philippines -- as well as the one with the 27-nation EU.

Beijing says it wants to see "reciprocity" in its trade with the United States. Foreign ministry spokesman Guo Jiakun said dialogue was need "to reduce misunderstandings".

The previous round of of China-US talks was held in London.

Analysts said many of the trade deals Trump has been publicising were leaning more on optics than on details.

Stephen Innes, managing partner at SPI Asset Management, a firm that advises on currency exchange and commodities, said an extension of the 90-day truce between China and the United States could reinforce that view.

"That truce could set the stage for a Trump - (President) Xi (Jinping) handshake later this year -- another risk-on carrot for markets to chew," he said.