Shanghai, Jul 31 (AFP) Chinese and US trade negotiators will bid to bring an end a year-long trade war that has seen both tariffs and insults flung between the world's two largest economies when they meet for official talks in Shanghai Wednesday.

US Trade Representative Robert Lighthizer and Treasury Secretary Steven Mnuchin arrived in China's financial capital on Tuesday, and were believed to have joined Chinese officials for dinner and informal discussions.

Washington and Beijing have so far hit each other with punitive tariffs covering more than USD 360 billion in two-way trade in a tense stand-off centred on demands for China to curb the alleged theft of American technology and provide a level playing field to US companies.

But even as the two teams were understood to have been meeting to salvage the trade talks, US President Donald Trump took to Twitter to slam China.

"My team is negotiating with them now, but they always change the deal in the end to their benefit," Trump tweeted.

The meetings on Wednesday will be the first face-to-face discussions since the US leader agreed to a truce with Chinese President Xi Jinping in June -- Trump had accused China of reneging on its commitments when previous talks broke down in May.

This time the US leader said Beijing was supposed to start buying US agricultural products but they have shown "no signs that they are doing so".

"That is the problem with China, they just don't come through," he said on Twitter Tuesday, hitting an already-tense relationship between the two countries.

Analysts said Trump's tweets will do little to ease the already-tense relationship between Washington and Beijing.

"Whatever shred of optimism markets had about the ongoing trade negotiations were dealt as a severe blow when President Trump flew off the handle again at China for not buying American agricultural products," said Stephen Innes, Managing Partner VM Markets Singapore.

"(The tweets show) Trump seems eager to get a deal, that shows his weakness," said Shanghai-based professor Shen Dingli.

Days before the Shanghai meeting, Trump threatened to pull recognition of China's developing nation status at the World Trade Organization, which Beijing called "arrogance".

State news agency Xinhua admitted in a commentary the day the trade officials arrived in China that relations were "strained" and called for the US to "treat China with due respect if it wants a trade deal".

The kick-starting of trade negotiations is still being seen as positive -- even if little of substance is expected -- following a truce agreed between Trump and Chinese President Xi Jinping at the G20 in June.

However, expectations were low, and trade officials on both sides kept an exceptionally low profile as they arrived for the talks.

US trade negotiators entered and left their hotel on Shanghai's famous waterfront through side doors without going through public areas, and did not stop to speak to the press or show their faces.

The city's Peace Hotel, a famous hotspot and tourist attraction where the two sides were believed to have met for dinner on Tuesday evening, closed its doors to all visitors ahead of the US motorcade arriving.

There was a heavy police presence which cleared the roads and the cars drove directly into the side entrance.

There was no sign of the rhetoric letting up either, with the China Daily newspaper's Tuesday editorial saying "the US should give its go-to tactic of maximum pressure a couple of days off as it has proven ineffective against China".

Vice Premier Liu He will likely again lead the series of official talks for China, together with Chinese Commerce Minister Zhong Shan. (AFP)

(This is an unedited and auto-generated story from Syndicated News feed, LatestLY Staff may not have modified or edited the content body)