Stocks snapped a four-day winning streak Thursday after a report said President Donald Trump would support moving ahead with additional tariffs on Chinese imports as early as next week.
Wall Street also looked ahead to a U.S.-Canada trade deal deadline set for Friday.
The Dow Jones Industrial Average dropped 137.65 points to 25,986.92 while the S&P 500 fell 0.4 percent to 2,901.13. The Nasdaq Composite declined 0.3 percent to 8,088.36 after reaching a record high. The indexes also closed lower for the first time in five sessions.
Bloomberg News reported that Trump told aides he supports moving forward with proposed tariffs on an additional $200 billion in Chinese goods. The report also said, however, that Trump has not made up his mind on the matter. The White House declined to comment on the report.
Strategists had told CNBC that the additional tariffs were the biggest risk for the market heading into September. Phil Blancato, CEO of Ladenburg Thalmann Asset Management, called U.S.-China trade relations "the unknown" in the market.
Investors also watched as the U.S. and Canada tried to strike a deal on trade.
"We had some momentum when the U.S and Mexico struck a deal earlier in the week," said Ryan Nauman, market strategist at Informa Financial Intelligence. "But as the deadline approaches, people are getting a bit worried."
Canada has until Friday to join a trade deal made between the U.S. and Mexico, according to Trump. However, Trump said he was confident an agreement between the two nations was within reach. "I think Canada very much wants to make the deal," Trump told reporters on Wednesday. "It probably won't be good at all if they don't."