Such a move could undermine one of the foundations of the modern global trading system, which the United States was instrumental in creating.
"If they don't shape up, I would withdraw from the WTO," Trump said.
Trump has complained the United States is treated unfairly in global trade and has blamed the WTO for allowing that to happen. He has also warned he could take action against the global body, although he has not specified what form that could take.
Bloomberg News also reported Thursday that Trump is ready to increase trade tensions with China, telling aides he wants to impose tariffs on $200 billion more in Chinese imports after a comment period ends next week.
The White House declined to comment on the Bloomberg report.
The report, which cited six unidentified sources, pressured markets. The S&P hit session lows and U.S. Treasury yields fell.
Some sources said Trump had not made his final decision, the report said.
The world's two largest economies have already applied tariffs to $50 billion of each other's goods in a tit-for-tat trade war. Talks aimed at easing tensions ended last week without major breakthroughs.
The new proposed tariffs would affect consumer products including home building supplies, technology products, bicycles and apparel.
A public comment period on the proposal is set to end on Sept. 6, and Trump plans to impose the tariffs after that deadline, Bloomberg said.
The U.S. president on Thursday also struck down a European Union proposal to eliminate tariffs on automobiles, calling it "not good enough."
Just hours earlier, the EU Trade Commissioner Cecilia Malmstroem had said the bloc was "willing to bring down... our car tariffs to zero" provided that the United States did the same.
"It's not good enough," Trump told Bloomberg News in an Oval Office interview, speaking of the Brussels offer.
"Their consumer habits are to buy their cars, not to buy our cars."
The White House in July sought to defuse the trade tiff when Trump and European Commission President Jean-Claude Juncker met and pledged to work towards a limited trade accord that would eliminate customs duties, but excluded the automobile sector.
Trump on Thursday also compared the EU to China.
"The European Union is almost as bad as China, just smaller," Trump said.
