Trump on Saturday told reporters that the talks had moved more slowly than he would have liked, but China wanted a deal more than he did.
The president also said there had been incorrect reporting about US willingness to lift tariffs on Chinese goods. Officials from China and the United States last week said the two countries had agreed to roll back tariffs already in place in a "phase one" trade deal.
The dollar index was last down 0.15% at 98.202. Against the euro, the dollar was 0.15% weaker at $1.103.
Mixed trade war headlines have left investors frustrated and confused, said Craig Erlam, senior market analyst at OANDA Corp. "We swing from optimism to pessimism on a daily basis and never feel any the wiser.
"This time it was Trump's turn to pour cold water on suggestions that not only is a deal in the offing, but it comes with the cherry on top that is the removal of tariffs. It's difficult to say who stands to lose more from this deal falling apart, but this last-minute jostling does not inspire confidence," Erlam said.
Although the US dollar often acts as a safe-haven asset in moments of political and economic uncertainty, it was lower on Monday against the Japanese yen and the Swiss franc, other traditional safe havens.
The dollar was 0.21% weaker against the Japanese currency, last buying 109.02 yen, and 0.42% weaker against the franc, at 0.993 per dollar.
The yen and franc were in favor as market participants reacted to the violent response to protests in Hong Kong, where police fired live rounds at protesters and at least one person was wounded.
The Chinese yuan weakened 0.3% to 7.009 per dollar in offshore trade.
The British pound was up 0.63% at $1.285 as the economy dodged an outright recession, although growth in the three months to September was slower than expected.
The British economy grew at its slowest annual pace in nearly a decade during the quarter as the global slowdown and Brexit worries hit manufacturing and business investment, official figures showed on Monday.