WASHINGTON (AFP, BLOOMBERG) - President Donald Trump said Thursday (March 14) that trade war negotiations with China should wrap up within four weeks and expressed optimism about striking a deal.

"We are doing very well with China talks," he told reporters. "We are getting what we have to get."

Later, at a Saint Patrick's Day celebration in the White House with the Irish Prime Minister Leo Varadkar, Trump predicted results in the near future.

"We'll have news on China probably - one way or way or the other, we're going to know over the next three to four weeks," Trump said.

"And then if one gets done, it will be something that people are going to be talking about for a long time because we have been really taken advantage of for a long time. And now I think - China, frankly, they've been very responsible and very reasonable."

Meanwhile China's state-run news agency Xinhua, in a brief report on Friday (March 15), said Chinese Vice-Premier Liu He had spoken by telephone with both US Treasury Secretary Steven Mnuchin and US Trade Representative Robert Lighthizer and the two sides made further substantive progress on trade talks.

It gave no other details, other than describing it as a third telephone call.

Despite Trump's upbeat assessment, the two sides continue to lock horns on the hugely complex dispute between the world's biggest economies. Earlier this week, Trump said there was still no plan for him to hold a summit with Chinese leader Xi Jinping.

Trump said Wednesday he is "in no rush" for a deal but that there is "a very good chance" for one.

Mnuchin told a congressional committee earlier Thursday that he expects the deal to be finalised soon, but cautioned that the process is complex.

"We are working diligently but there are 150 pages documents that we are working on," Mnuchin said in response to a question.

The accord will include "very clear enforcement provisions and we want to get the agreement right," he said. "That's more important that the exact timing."

Trump had said he expected to hold a summit with Xi Jinping late this month at his Florida golf resort.

But three people familiar with the matter said a meeting between Mr Trump and Mr Xi to sign an agreement to end their trade war won't occur this month and is more likely to happen in April at the earliest.

Despite claims of progress in talks by both sides, a hoped-for summit at Trump's Mar-a-Lago resort will now take place at the end of April if it happens at all, according to one of the people.

China is pressing for a formal state visit, which traditionally takes place in Washington, rather than a lower-key appearance just to sign a trade deal, the person said.

Xi's staff have scrapped planning for a potential flight to the US following a trip to Europe later this month, a separate person said. The people asked not to be named as the details are private.

Stocks edged lower and the dollar gained as investors weighed fresh developments in trade talks between the world's two largest economies.

Lighthizer this week pointed to "major issues" still unresolved in the talks, with few signs of a breakthrough on the most difficult subjects.

Chinese officials have also bristled at the appearance of the deal being one-sided, and are wary of the risk of Trump walking away even if Xi were to travel to the US.

The White House communications staff didn't immediately respond to a request for comment. The State Council in Beijing also didn't respond to a request for comment.

Trump himself has dialed down the urgency of getting a deal signed as early as this month. He acknowledged concerns in Beijing about the possibility of him walking away from a trade deal, offering to push back a summit with Xi until a final agreement is reached.

"We could do it either way," Trump told reporters Wednesday at the White House. "We can have the deal completed and come and sign or we can get the deal almost completed and negotiate some of the final points. I would prefer that. But it doesn't matter that much."

Signing Summit

There is currently no plan for the US to send another lower-level delegation to Beijing to iron out the details but it's possible Lighthizer would have to make the trip again to finalise some of the outstanding points in person.

The negotiations have zeroed in on the phasing out of joint-venture requirements, the deal's enforcement mechanism and the lifting of tariffs the two sides have imposed on each other, the people familiar with the talks said. Those topics are negotiated at the ministerial level.

While gaps have narrowed on a number of issues, a lot of work remains. The countries exchanged drafts in English only and China now needs to translate the document and complete a so-called legal scrub, the people added.