Donald Trump has said he will meet Chinese president Xi Jinping soon to try to seal a comprehensive trade deal as the US president while China’s trade delegation said the two sides had “clarified a timetable and roadmap” for the next negotiations.

Trump, speaking at the White House on Thursday during a meeting with Chinese vice premier Liu He, said he was optimistic the world’s two largest economies could reach “the biggest deal ever made”.

No specific plans for a meeting with Xi were announced, but Trump said there could be more than one meeting. US trade representative Robert Lighthizer and Treasury secretary Steven Mnuchin were invited to bring a negotiating team to Beijing in mid-February, with dates still pending.

At the end of two days of high-level talks next door to the White House, Liu told Trump China would make a new, immediate commitment to increase soybean purchases. An administration official later clarified the amount as a total of 5m tonnes, in effect doubling the amount bought by China since resuming limited purchases in December.

According to state news agency Xinhua, the Chinese delegation agreed to “vigorously expand” imports of US agricultural products, energy products, industrial manufactured goods, and service products.

“The leaders of the two sides had frank, concrete and constructive discussions on issues of trade balance, technology transfer, intellectual property protection, implementation mechanisms… and made important progress,” Xinhua said.

US soybean sales to China, which totalled 31.7m tonnes in 2017, were largely cut off in the second half of last year by China’s retaliatory tariffs. The latest announcement drew a positive reaction from Trump, who said it would “make our farmers very happy”.

While China has offered increased purchases of US farm, energy and other goods to try to resolve the trade disputes, negotiators dug into thornier issues, including US demands that China take steps to protect American intellectual property and end policies that Washington says force US companies to turn over technology to Chinese companies.

Lighthizer said there was “substantial progress” on these issues, including verification mechanisms to “enforce” China’s follow-through on any reform commitments it makes.

“At this point, it’s impossible for me to predict success. But we’re in a place that if things work out, it could happen,” Lighthizer said at the Oval Office meeting.

Later, he said the US objective was to make China’s commitments “more specific, all-encompassing and enforceable” with a mechanism for taking action if China failed to follow through, but declined to provide specific issues.

Reuters previously reported that such an enforcement mechanism would involve a snap-back of US tariffs.

Asked whether the two sides discussed lifting US tariffs on Chinese goods, Lighthizer said tariffs were not part of the talks.

A person familiar with the discussions said a broad range of concerns about access to Chinese agricultural markets were raised in the talks but little progress was made.

The White House said in a statement a scheduled tariff increase on 2 March on $200bn of Chinese goods from 10% to to 25% was a “hard deadline” if no deal was reached by 1 March.

Trump said he did not think he would need to extend the deadline. “I think when President Xi and I meet, every point will be agreed to,” Trump added.

But Trump has vetoed multiple proposed trade deals with China, choosing to push ahead with tariffs on Chinese goods to gain leverage. Earlier, Trump said on Twitter he was looking for China to open its markets.

The U.S. complaints on technology transfers, and intellectual property protections, along with accusations of Chinese cyber theft of American trade secrets and a systematic campaign to acquire U.S. technology firms, were used by Trump’s administration to justify punitive tariffs on $250 billion worth of Chinese imports.

China has retaliated with tariffs of its own, but has suspended some and is allowing some purchases of U.S. soybeans during the talks.