WASHINGTON — President Ronald Reagan once likened trade wars to the pie fights in old Hollywood comedies. One pie in the face leads to another. And then another.

Pretty soon, Reagan said in a 1986 radio address, “everything and everybody just gets messier and messier. The difference here is that it’s not funny. It’s tragic. Protectionism becomes destructionism. It costs jobs.”

Suddenly, the world’s financial markets are gripped by fear that an escalating trade rift between the United States and China — the  two mightiest economies — could smear the world with a lot of splattered cream and broken crust. If it doesn’t prove tragic, as Reagan warned, it may still inflict far-reaching pain.

The Dow Jones industrial average lost a combined nearly 1,150 points Thursday and Friday after President Donald Trump set his administration on a path to restrict Chinese investment in the United States and impose tariffs on up to $60 billion of Chinese products.

“We should be very worried,” said Bryan Riley, director of the conservative National Taxpayer Union’s Free Trade Initiative. “It’s very possible this could escalate into something that neither country intends.”

The trade sanctions that Trump unveiled Thursday are meant to punish Beijing for pilfering technology from American companies or for forcing them to hand over technology in exchange for access to China’s market.