Donald Trump suggested that China "should probably wait out our Election" (File Photo)

US President Donald Trump warned China Tuesday against waiting to complete a trade deal with Washington, just as negotiations began in Shanghai to resurrect stalled talks with Chinese officials.

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

"China is doing very badly, worst year in 27 - was supposed to start buying our agricultural product now - no signs that they are doing so. That is the problem with China, they just don't come through."

The negotiations are the first face-to-face talks since Trump agreed to a truce with Chinese President Xi Jinping at June's G20 summit.

Washington and Beijing have so far hit each other with punitive tariffs covering more than $360 billion in two-way trade.

The US economy "has become MUCH larger than the Chinese Economy is last 3 years," Trump boasted.

The US president suggested that China "should probably wait out our Election to see if we get one of the Democrat stiffs like Sleepy Joe. Then they could make a GREAT deal, like in past 30 years, and continue ... to ripoff the USA, even bigger and better than ever before."

The reference is to the 2020 presidential election and former US vice president Joe Biden, the current Democratic Party front runner for the nomination.

"The problem with them waiting, however, is that if & when I win, the deal that they get will be much tougher than what we are negotiating now... or no deal at all. We have all the cards, our past leaders never got it!" he added.

Trump later told reporters: "We're either going to make a great deal or we're not going to make a deal at all."

He also reiterated his belief that China wants to delay a deal until after next year's election.

They "pray that Trump loses and then they'll make a deal with a stiff," he said.