NEW YORK (AFP) - Wall Street stocks finished mixed Wednesday (March 7) as markets weighed conflicting signs on the Trump administration's trade plans following the departure of a key White House economic adviser.

The Dow Jones Industrial Average shed 0.3 per cent to 24,801.36.

The broad-based S&P 500 lost 0.1 per cent at 2,726.80, while the tech-rich Nasdaq Composite Index added 0.3 per cent at 7,396.65.

US stocks opened sharply lower on news that White House economic adviser Gary Cohn would depart the White House in the coming weeks after failing to persuade Trump on free trade issues. Trump has vowed to enact tariffs on imported steel and aluminium.

Cohn was regarded as "a moderate and business-friendly" figure who countered protectionist forces in the White House, said a note from Oxford Economics that warned of a potential trade war.

Cohn's exit represents a "watershed moment for US economic policy," Oxford Economics said.

But markets rallied somewhat late in the session after White House press secretary Sarah Sanders said there were "potential carve-outs for Mexico and Canada" and other countries based on national security.

JJ Kinahan, chief market strategist at TD Ameritrade, agreed that Cohn's departure was a loss, but cited Treasury Secretary Steven Mnuchin and Commerce Secretary Wilbur as Trump advisers who understood markets.

"Nobody knows what the tariffs are going to be," Kinahan said. "This administration tends to throw things out, get people riled up and then settle on something a bit more pragmatic. We'll see if that's the case here."

Among individual stocks, Dollar Tree dived 14.5 per cent after reporting same-store sales grew by less than expected in the fourth quarter.

Autodesk surged 14.9 per cent after the software company reported a 21.4 per cent jump in first-quarter revenue to US$480.7 million behind strong gains in subscriptions.