Beijing also is likely to seek removal of 15 per cent tariffs imposed on September 1 on around US$125 billion of Chinese goods, one of the sources said. Trump imposed the tariffs in August after a failed round of talks, effectively setting up punitive duties on nearly all of the US$550 billion in US imports from China.

“The Chinese want to get back to tariffs on just the original US$250 billion in goods,” the source said.

Derek Scissors, a resident scholar and China expert at the American Enterprise Institute in Washington, said the original goal of the early October talks was to finalise a text on intellectual property, agriculture and market access to pave the way for a postponement of the December tariffs.

“It’s odd that [the president] was so upbeat with Liu He and yet we still don’t have the December 15 tariffs taken off the table,” Scissors said.

US Treasury Secretary Mnuchin said last week no decisions were made about the December 15 tariffs, but added: “We’ll address that as we continue to have conversations.”

If a text can be sealed, Beijing in return would exempt some US agricultural products from tariffs, including soybeans and wheat and corn, a China-based source told Reuters. Buyers would be exempt from extra tariffs for future buying and receive returns for tariffs they already paid in previous purchases of the products on the list. But the ultimate amounts of China’s purchases are uncertain.

Trump has touted purchases of US$40-50 billion annually – far above China’s 2017 purchases of US$19.5 billion, as measured by the American Farm Bureau.

One of the sources briefed on the talks said that China’s offer would start out at around US$20 billion in annual purchases, largely restoring the pre-trade-war status quo, but this could rise over time. Purchases also would depend on market conditions and pricing.

Lighthizer has emphasised China’s agreement to remove some restrictions on US genetically modified crops and other food safety barriers, which the sources said is significant because it could pave the way for much higher US farm exports to China.

The high-level call comes a day after US Vice-President Mike Pence railed against China’s trade practices and construction of a “surveillance state” in a major policy speech. But Pence left the door open to a trade deal with China, saying Trump wanted a “constructive” relationship with China.

While the US tariffs on Chinese goods has brought China to the negotiating table to address US grievances over its trade practices and intellectual property practices, they have so far failed to lead to significant change in China’s state-led economic model.

The “phase one” deal will ease tensions and provide some market stability, but is expected to do little to deal with core US complaints about Chinese theft and the forced transfer of American intellectual property and technology. The intellectual property rights chapter in the agreement largely deals with copyright and trademark issues and pledges to curb technology transfers that Beijing has already put into a new investment law, people familiar with the discussions said.

More difficult issues, including data restrictions, China’s cybersecurity regulations and industrial subsidies will be left for later phases of talks, but some China trade watchers said that a completion of a “phase one” deal could leave little incentive for China to negotiate further, especially in a US election year in 2020.

“US-China talks change very quickly from hot to cold but, the longer it takes to nail down the easy phase one, the harder it is to imagine a phase two breakthrough,” said Scissors.

Two of the sources said that Mnuchin and Lighthizer would likely travel to Beijing at the start of November for further in-person talks to try to finalise a text, although a US Treasury spokesman said no such meeting had been planned.