Bellwether exporting and metal-using stocks Caterpillar and Boeing fell victim to the trade tariff controversy, weakening the Dow industrials.
"The big multinational, industrial companies of the world are all taking a hit on the concern that they will be the targets of reprisal sanctions", said Robert Phipps, a director at Per Stirling Capital Management in Austin.
At the close of trading in NY, the Dow Jones Industrial Average shed 157.13 points, or 0.6%, to 25,178.61, turning lower after rising as much as 113 points earlier in the session.
USA market indexes were mostly lower Wednesday.
The Canadian dollar closed at 77.94 cents U.S., up 0.06 of a United States cent.
Goldman Sachs gained 1.1 per cent after announcing that co-president Harvey Schwartz would retire, leaving David Solomon the sole president and next in line to become the investment bank's next chief executive.
DUP fury as Tusk says Ireland comes first in negotiations on Brexit
A legal challenge to force Theresa May to concede a second European Union referendum has been launched by anti-Brexit campaigners. He had been speaking in a debate with MEPs on the state of play of the Brexit negotiations earlier today.
Sterling rose on optimism that a Brexit transition deal might be agreed next week, after a junior minister said Britain was very close to sealing one with the European Union. "If such a deal does take place, however, it could be an important positive development for sterling in the near term by reducing "cliff-edge" risks", strategists at UBS said in a note.
The Treasury Budget was the only leading report on the economic calendar Monday.
The S&P/TSX composite index closed up 26.98 points to 15,604.79 on a day that saw gold and base metals move higher while energy stocks weighed on the market.
The initial strength in the market came as traders continued to react positively to the monthly jobs data released by the Labor Department on Friday.
Wall Street's main indexes closed up almost 2 percent on Friday after data showed USA job additions in February grew by a strong clip but wage growth was sluggish.
Traders of US short-term interest-rate futures kept bets the Federal Reserve will stick to three rate hikes this year.