Secretary of State Marco Rubio said the global financial markets will bounce back after plunging for a second day, following President Trump’s rollout of a fresh set of tariffs.

Rubio said Friday during a press conference in Brussels that businesses “just need to know what the rules are.”

“Once you know what the rules are, they will adjust to those rules. So I don’t think it’s fair to say economies are crashing. Markets are crashing because markets are based on the stock value of companies who today are embedded in modes of production that are bad for the United States,” the U.S.’s top diplomat said while in Brussels for a meeting with NATO foreign ministers.

On Wednesday, Trump reset the U.S. trade agenda by announcing a 10 percent flat-rate tariff on all goods coming into the country. He also rolled out targeted tariffs for scores of other countries, with duties going as high as 54 percent.

Trump said the U.S. and its “taxpayers have been ripped off for more than 50 years, but it’s not going to happen anymore.”

A day later, stock indexes fell along with the value of the U.S. dollar. Some Republican senators said they were shocked at the scale of tariffs aimed at U.S. allies and trading partners.

“There’s a lot that I certainly don’t know,” Sen. Lisa Murkowski (R-Alaska) said Thursday. “How long are they going to last? There’s a lot of uncertainty.”

“One of the things that I’m hearing from folks back home is they’re certainly afraid about what it’s going to mean for price increases, very afraid about that,” the senator added.

Rubio argued that the U.S., despite being the largest consumer market on the planet, “only” exports service, declaring that change is needed.

“The president rightly has concluded that the current status of global trade is bad for America and good for a bunch of other people. And he’s going to reset it, and he’s absolutely right to do it,” he said.