The Commerce Department has started an investigation into the impact of uranium imports on U.S. national security, a move that could limit future imports and add another front to the Trump administration’s trade fight.

Commerce Secretary Wilbur Ross said Wednesday that the United States produces just 5 percent of the uranium it needs for the U.S. military and for electricity generation, down from nearly half in 1987.

The probe follows an earlier national security investigation into steel and aluminum imports, which resulted in steep 25 percent duties on shipments of the metals from the European Union, Canada, Mexico, China and Japan.

A second investigation, focused on the threat to security posed by auto imports, is ongoing.

Those investigations are unusual in their reliance on a national security justification for limiting imports in such broad categories — or potentially limiting them, in the case of autos — from close U.S. allies.

Two U.S. uranium mining companies, UR-Energy and Energy Fuels, requested the investigation in January. They argued that the U.S. uranium industry has been decimated by imports from state-supported companies in Russia, Kazakhstan, Uzbekistan and China.

The U.S. Energy Information Administration said in May that uranium production plummeted in the first quarter of this year to 226.8 million pounds. That is 50 percent lower than just a year earlier. The two companies say it is the lowest level since the late 1940s. As recently as the first three months of 2014, U.S. production was 1.2 million pounds.

“Our country cannot afford to depend on foreign sources — particularly Russia, and those in its sphere of influence, and China — for the element that provides the backbone of our nuclear deterrent, powers the ships and submarines of America’s nuclear Navy, and supplies 20 percent of the nation’s electricity,” the petition from the two companies said.

Energy Fuels and Ur-Energy produce more than half of U.S. uranium. But they say they have laid off roughly half of their combined employees and are operating at just 9 percent and 13.5 percent of capacity, respectively.

The companies asked the government to place a quota on imports that would preserve one-quarter of the U.S. market for domestic uranium. They also requested the government implement a “Buy America” policy for government agencies that use uranium.

The investigation can take as long as nine months, after which Ross can recommend steps for the president to take.

(AP)