A bipartisan group of U.S. Senate and House members sent a letter Wednesday urging the U.S. Department of Veterans Affairs (VA) to let its doctors discuss and recommend medical marijuana as a treatment in states where it is legal.

The letter to VA Secretary Robert McDonald comes four days before the expiration of a current directive that prohibits VA physicians from recommending the plant for medicinal purposes.  

“According to the current directive, VA providers are prohibited from completing forms seeking recommendations or opinions regarding a veteran’s participation in a state-sanctioned marijuana program,” the letter reads in part. “This policy disincentivizes doctors and patients from being honest with each other.”

The group argues that VHA Directive 2011-004, which expires on Sunday, discourages veterans from having frank discussions with their doctors for fear of losing benefits.

Senators Kirsten Gillibrand (D-N.Y.), Steve Daines (R-Mont.) and Jeff Merkley (D-Ore.) and Representatives Earl Blumenauer...