Investor hopes of a "phase one" trade deal have been a key factor supporting stocks recently, but Trump said on Saturday that the United States would only make a trade deal if it was the "right deal" for America, adding that the talks had moved more slowly than he would have liked.
Violence in Hong Kong during protests also cast a shadow on sentiment after the three major averages posted all-time closing highs on Friday, and the benchmark S&P 500 tallied its fifth week of gains in a row.
"You had negative headlines that were a reason for consolidation after five weeks in a row where stocks moved higher," said Willie Delwiche, investment strategist at Baird in Milwaukee.
"The biggest risk right now is excessive optimism," Delwiche said. "And so if we can have a few days of consolidation where it eases some of that, then that’s a healthy development for the market overall."
Michael Arone, chief investment strategist at State Street Global Advisors, said that "a lot of good news is priced into the stock market," including the Federal Reserve's interest-rate cuts, third-quarter earnings topping low expectations, signs of a bottoming of economic data, and enthusiasm about a potential resolution to trade tensions.
Investors will be watching for any trade commentary from Trump on Tuesday, when he is expected to speak at The Economic Club of New York.
The Dow Jones Industrial Average rose 10.25 points, or 0.04%, to 27,691.49, the S&P 500 lost 6.07 points, or 0.20%, to 3,087.01 and the Nasdaq Composite dropped 11.04 points, or 0.13%, to 8,464.28.
Shares of Boeing Co jumped 4.5% to $366.96 after the planemaker said it expected U.S. regulators to approve the return to commercial service of its grounded 737 MAX jet in the coming weeks, and expects commercial service to resume in January.
Boeing shares are the biggest weight in the 30-component, price-weighted Dow, helping the blue-chip index tally another record close on Monday.
Walgreens Boots Alliance Inc shares gained 5.1% after Bloomberg reported that KKR & Co had formally approached the drugstore giant for what could be the biggest-ever leveraged buyout.
Most of the S&P 500 sectors ended in the red, with utilities, energy and healthcare falling the most.
Investor attention will shift to economic data and testimony by Fed Chair Jerome Powell on the economic outlook later this week, while a handful of big companies, including Walmart Inc, Cisco Systems Inc and Nvidia Corp, will report earnings.
The third-quarter corporate reporting season, which is drawing to a close, has been better than expected overall, but S&P 500 companies are still expected to have posted a 0.5% decline in earnings, according to Refinitiv data.
Declining issues outnumbered advancing ones on the NYSE by a 1.36-to-1 ratio; on Nasdaq, a 1.17-to-1 ratio favored decliners.
The S&P 500 posted 19 new 52-week highs and one new low; the Nasdaq Composite recorded 64 new highs and 96 new lows.
About 5.5 billion shares changed hands in U.S. exchanges, below the 6.8 billion-share daily average over the last 20 sessions.
By Lewis Krauskopf