Trump's trade chief is warning new tariffs are coming as temporary 10% global duties expire

"We expect to see some action soon," Greer said on CNBC's "Squawk Box" in response to a question about whether additional tariffs were on the horizon. Greer said he could not specify a timeline, citing obligations to brief Congress and other stakeholders before making any formal announcement. "But we do expect action soon," he added.

The 10% across-the-board tariff Trump put in place in February relied on Section 122 of the Trade Act of 1974 and came just hours after the Supreme Court invalidated his "liberation day" tariff regime. Those Section 122 tariffs are set to lapse at 12:01 a.m. ET Friday, with little indication that Congress will act to extend them.

The Trump administration has already been working to replace that authority. USTR put forward a new round of duties in early June, proposing rates as high as 12.5% on goods from 60 economies, with the action grounded in Section 301 authority and justified by claims of widespread forced-labor practices abroad. Greer said those proposed duties would cover "about 99% of our trade."

"The U.S. has laws to prohibit trading goods with forced labor," Greer said. "Other countries, most don't have a law. Those that do don't really enforce it."

According to Reuters, any tariffs announced in the near term would likely match the current 10% level, though the administration was pursuing parallel investigations aimed at building a legal basis for steeper rates down the line. The administration was also working on additional investigations that could provide legal authority to propose higher duties.

The tariff activity comes as the administration has been rebuilding its trade regime through Section 301, an authority it has used in a series of country-specific actions in recent weeks. The administration imposed 25% tariffs on most imports from Brazil, effective July 22, citing policies the U.S. says harm American workers across sectors including digital trade, intellectual property, and ethanol. Brazil also faces a separate Section 301 inquiry focused on forced labor, with a ruling anticipated by July 24 that could bring its total tariff exposure to 37.5%.

Trump also signed three proclamations Monday imposing 50% tariffs on certain Canadian goods, targeting motor vehicles, alcoholic beverages, and dairy products. Those tariffs take effect August 19 and cover roughly $20 billion in Canadian imports.