Wall Street stocks fell again on Tuesday as markets await a Federal Reserve decision on interest rates while anticipating US trade deal breakthroughs that have yet to materialise.

Canadian Prime Minister Mark Carney told US President Donald Trump that his country was "never for sale" at a White House meeting that underscored tensions after the United States imposed tariffs on Canada and other trading partners.

The market "seems to be disappointed over the fact that we're not hearing any trade deal news," said Art Hogan of B Riley Wealth Management.

Stocks had risen most of the last two weeks in anticipation of progress on the trade front. But major US indices spent the entire Tuesday session in the red, with the Dow Jones finishing down one percent at 40,829.

The S&P 500 declined 0.8 percent to 5,606, while the Nasdaq fell 0.9 percent to 17,689.

Data released on Tuesday showed the overall trade deficit for the United States jumped 14.0 percent to US$140.5 billion for March, a record for a month.

Pharmaceutical and biotech stocks took a beating due to the appointment of oncologist Vinay Prasad to a top post at the US Food and Drug Administration. Prasad has been an outspoken critic of the agency's prior approach to Covid-19 vaccines and other key decisions.

Merck and Pfizer both fell more than four percent while Moderna sank more than 12 percent.

Ford rose 2.7 percent after reporting a 65 percent drop in profits that nonetheless topped estimates. The carmaker suspended its forecast amid tariff uncertainty.

Mattel climbed 2.8 percent as it also suspended its outlook, citing uncertainty due to the "volatile macro-economic environment and evolving US tariff landscape."

Markets are looking ahead to Wednesday's Fed decision. The US central bank is widely expected to pause again on interest rate changes and wait for clarity on the economic impact of Trump's tariff rollout.

Trump has aggressively argued that the Fed should resume interest rate cuts. (AFP)