The United States on Wednesday began investigating whether uranium imports threaten national security, launching a process that could see yet more tariffs imposed on exports from allied countries.
Commerce Secretary Wilbur Ross announced the probe would cover the entire uranium sector, including mining and enrichment, and both defense and industrial uses.
‘Our production of uranium necessary for military and electric power has dropped from 49 percent of our consumption to five percent,’ Ross said in a statement.
He pledged a thorough, fair and transparent investigation of the matter. 
Ross formally notified Defense Secretary Jim Mattis on Wednesday of the decision, according to a letter released by the Commerce Department.
Washington has outraged major US trading partners such as Canada and the European Union by citing national security concerns as justification to impose tariffs on steel and aluminum – touching off a wave of countermeasures against US agriculture and other goods and alarming lawmakers and industry.
The Commerce Department in May began a similar process to determine whether the hundreds of billions of dollars worth of autos and parts imported every year jeopardize US national security.
The United States imported $1.4 billion worth of enriched uranium last year, along with $470 million in uranium ores and $1.8 billion in uranium compounds and alloys, according to Commerce Department data.
Canada and Kazakhstan account for about half of the imported uranium used in US power generation, according to the Energy Department.
Other major sources include Australia, Russia and Uzbekistan.
The Commerce Department is undertaking the probe following petitions in January from two American miners: Ur-Energy and Energy Fuels.
Uranium accounts for 20 percent of US electricity generation and is used to power submarines and aircraft carriers, but domestic production accounts for only five percent of US needs, according to the department.
According to the Energy Department, as prices tumbled to just over $25 per pound (450 grams) between 2009 and 2015, employment in the sector fell more than 60 percent, to just over 600 workers.