Specialist Mario Picone, right, works with traders at his post on the floor of the New York Stock Exchange, . U.S. stocks moved broadly lower in early trading on Wall Street Tuesday as President Donald Trump ramped up criticism of China just as negotiators began a new round of trade talksFinancial Markets Wall Street, New York, USA - 30 Jul 2019

They may have only just got back on track after falling apart, but are make or break trade negotiations between the U.S. and China already faltering again?

As talks between the two superpowers resume this week in Shanghai, President Trump ratcheted up pressure this morning, accusing the Chinese of not following through with previous commitments and stating that if a deal is not made soon then he will toughen his requirements if reelected next year.

“My team is negotiating with them now, but they always change the deal in the end to their benefit,” he tweeted, citing China’s slowness to buy U.S. agricultural products as promised. “They should probably wait out our election to see if we get one of the Democrat stiffs like Sleepy Joe,” referring to Democratic candidate and former vice president Joe Biden.

“The problem with them waiting is that if and 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.

His comments come as U.S. Trade Representative Robert Lighthizer and Treasury Secretary Steven Mnuchin are due to meet with Chinese negotiators this week and will stoke concerns that proposed tariffs on a raft of goods, including apparel and footwear, could be put back on the table.

In addition to increased fears of a hard Brexit, Trump’s tough rhetoric appeared to weigh on stocks in early-morning trading. The Dow Jones Industrial Average was down 0.4 percent, while the S&P 500 slipped 0.5 percent.

This is despite hopes among traders that the Federal Reserve will this week move to cut interest rates in a bid to cushion the U.S. economy from the fallout from the trade dispute, as well as a weakening global economic backdrop.