A bipartisan group of 45 senators has sent a letter to U.S. Secretary of Defense Jim Mattis urging him to advise President Tump against implementing a proposed ban on allowing transgender Americans to serve openly in the U.S. military.

The letter was introduced and circulated by U.S. Sen. Kirsten Gillibrand (D-N.Y.) and signed by 42 other Democrats, Independent Sen. Bernie Sanders (Vt.) and Republican Sen. Susan Collins (Maine).

In their letter, the senators say the president’s proposal contradicts existing Defense Department policies, undermines military readiness, and puts those out transgender service members who are currently serving at risk of being discharged.

Trump made the announcement of the ban on Wednesday via Twitter, which reportedlytook Mattis and others at the Department of Defense by surprise. Thus far, the Department of Defense has not received formal guidance on how to implement this shift in policy, according to Politico.

As a result, the department has not yet modified its existing policy, which, despite a six-month delay, has been moving toward allowing new transgender recruits to begin serving openly starting next year. Read more via Metro Weekly