President Donald Trump threatened to impose tariffs on every single Chinese import into America as the world’s two largest economies exchanged the first blows in a trade war that isn’t set to end anytime soon.

After months of rhetoric, a 25 percent levy on $34 billion of Chinese goods entering the U.S. took effect just after midnight Washington time on Friday with farming plows and airplane parts among the products targeted. China hit back immediately via duties on U.S. shipments including soybeans and automobiles.

Neither side shows any signs of backing down. Trump is already eyeing another $16 billion of Chinese goods and suggesting the final total could top $500 billion, more than the U.S. bought in 2017. China’s Commerce Ministry accused the U.S. of “bullying” and igniting “the largest trade war in economic history.”

The first ever U.S. tariffs aimed just at China will likely rally Trump’s voters who agree with his “America First” argument that Beijing hasn’t played fair for years, stealing America’s intellectual property and undercutting its manufacturers.

But the risk is that a spiraling conflict undermines economic growth by gumming up international supply chains and inflicting higher prices on companies and consumers.

The Federal Reserve has already noted some firms are slowing investment, while Harley-Davidson Inc. and General Motors Co. are warning they may cut jobs.

Given the moves were well flagged, investors took them in their stride. European stocks trimmed gains and U.S. equity-index futures fluctuated.

The dollar and Treasuries edged lower as traders looked ahead to the release of U.S. jobs data.

“Clearly the first salvos have been exchanged and in that sense, the trade war has started,” said Louis Kuijs, chief Asia economist at Oxford Economics. “There is no obvious end to this.”

The extent of the economic damage will depend on how far both sides go. If the U.S. and China cool off after a first round of tariffs, the fallout will be modest, according to Bloomberg Economics.

Under a full-blown trade war in which the U.S. slaps 10 percent tariffs on all other countries and they respond, the economists reckon U.S. growth would slow by 0.8 percentage point by 2020.

Trump has already imposed duties on foreign steel and aluminum imports, drawing a response from the European Union and Canada which fret he may go after automakers next.

“Our view is that trade war is never a solution,” Chinese Premier Li Keqiang told reporters during a trip to Bulgaria. “No one will emerge as a winner from trade war, it benefits no one.”