A lack of trust between Beijing and Washington is hampering the conclusion of an interim trade deal, with China doubting whether it can rely on any agreement made with President Donald Trump and the US unconvinced Beijing will deliver on promised reforms, according to former US government officials.

Christopher Hill, former US assistant secretary of state for East Asian and Pacific affairs, said that both nations recognised the need to get the "phase one" deal done, but he warned that both had "a mountain of mistrust" standing in the way of an agreement.

"Mistrust is the most difficult thing to remove from the negotiation," said Hill, a longtime negotiator who represented the US between 2005 and 2007 in the six-party talks to press North Korea to abandon its nuclear weapon programme.

"China's concerned that they can't really reach a deal because they can't rely on it. On the US side, there is a perception that China also has credibility problems," Hill told the South China Morning Post on the sidelines of an economic forum in Sanya, in the southern Chinese province of Hainan over the weekend.

"If I'm China, I would be concerned whether the deal Trump agrees to is the one he agreed to tomorrow and the next day. If I'm Trump, I would see the big problem for me is to convince China that what I offer is really what I will stand by [and] that is my word," he said.

Officials from the two sides are rushing to conclude negotiations before Sunday, when the US is set to impose additional tariffs on Chinese imports. While a phase-one deal is unlikely to be reached by then, sources close to the talks said they did not expect the new tariffs to come into force.

China and the US were believed to have reached an agreement in May to end the costly trade war, which began in July 2018. But talks collapsed suddenly, with the US accusing China of backtracking on concessions and Beijing accusing Washington of flip-flopping and making unreasonable demands, such as expecting China to change its state-led economic development model.

Former US treasury secretary Jack Lew said leaders in both countries should take a step back to find the right pathway.

"One of the problems is, I don't know that teams from our country speak for our president in those meetings," he said in an address to the forum, adding that during his term as treasury secretary, from 2013 to 2017, he had the backing of then-US President Barack Obama.

"I know when I attended these meetings I spoke with authority and we worked through whether there would be an agreement on exchange rates or agreement on information technology, or agreements on decreasing subsidies," he said.

"It's been a problem in these talks that our teams have gone through many rounds where it's not clear what ultimately would be the president's position. That makes it hard for the negotiation."

Steve Orlins, president of the National Committee on US-China Relations, observed disappointment and confusion in the Chinese leadership over what Trump did and wanted, including on the trade surplus and structural reform.

"You don't know what the [Trump] administration is demanding. They have not been very transparent on what China needs to do to satisfy that," he said.

But he also pointed out the growing dissatisfaction in the US over China's promises and urged Beijing change, from creating a level playing field to intellectual property protection to the subsidies given to state-owned enterprises.

"The Americans talk about this in terms of promise fatigue. The concept of promise fatigue is you promise something 20 times and, by the 20th time, if you don't get it, you kind of go 'Ha, I'm never going to get it,'" he said.

Hill said current efforts by both sides to de-escalate tensions were not enough.

"I do believe that the US and China need to make a bigger effort to find areas of agreement, which is not to solve the areas of disagreement, but to establish some patterns where we can work with China, and I think those patterns can carry on into areas where we currently disagree, and I don't think there's been enough effort," he said.

This article originally appeared in the South China Morning Post (SCMP), the most authoritative voice reporting on China and Asia for more than a century. For more SCMP stories, please explore the SCMP app or visit the SCMP's Facebook and Twitter pages. Copyright © 2019 South China Morning Post Publishers Ltd. All rights reserved.

Copyright (c) 2019. South China Morning Post Publishers Ltd. All rights reserved.