President Trump is set to announce broad-based tariffs on steel and aluminum imports on Thursday afternoon using a legal provision that allows the imposition of import taxes on national security grounds.

“Our military and intelligence communities benefit from these alliances and partnerships, and in today’s strategic environment it is of utmost importance that we continue to foster constructive relationships with international partners that share our nation’s concerns and interests with emphasis on addressing the most critical challenges facing the U.S. and global steel industry,” the letter said.

“We remain concerned that imposing tariffs risks alienating key international partners that contribute to our ability to defend our nation and maintain international stability,” the letter continued.

The letter was signed by a total of seven GOP senators, including John Barasso (Wyoming), a member of the Senate GOP leadership team.