A group of six progressive U.S. senators criticized the Biden administration's "extraordinarily disappointing" response on Wednesday to their request last year to remove marijuana from Schedule I of the Controlled Substances Act, a category reserved for drugs that have no accepted medical use. 

The Justice Department took six months to provide the senators with a half-page response that simply said the Department of Health and Human Services doesn't recognize marijuana as a safe treatment for any disease or condition, a determination that the senators took issue with. 

"It is obvious that cannabis has widely accepted medical benefits, affirmed by medical and scientific communities both here and across the globe," Sens. Elizabeth Warren, D-Mass., Cory Booker, D-N.J., Kirsten Gillibrand, D-N.Y., Ed Markey, D-Mass., Ron Wyden, D-Ore., and Bernie Sanders, I-Vt., wrote in the letter to the president. 

"The therapeutic properties of cannabis caused by the effects of both the tetrahydrocannabinol-alpha (THC) and cannabidiol (CBD) components make it an excellent alternative to highly addictive opiates for pain relief." 

Marijuana is weighed and packaged

Marijuana is weighed and packaged for sale at the Northwest Patient Resource Center medical marijuana dispensary in Seattle. (Associated Press)

Biden pledged to decriminalize marijuana and automatically expunge past convictions related to the drug while on the campaign trail in 2020, but his administration's inaction on marijuana policy has frustrated the progressive flank of the Democratic Party. 

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The House voted 220-204 to decriminalize marijuana at the federal level in April, with three Republicans voting yes and two Democrats voting no, but the legislation has stalled in the Senate. 

The six progressive senators wrote in Wednesday's letter that the president should take executive action to also issue pardons for anyone convicted of a nonviolent offense related to marijuana.

Jar of marijuana

A jar containing a strain of marijuana nicknamed "Killer D" at a medical marijuana facility in Unity, Maine. (AP Photo/Robert F. Bukaty)

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"The Administration’s failure to coordinate a timely review of its cannabis policy is harming thousands of Americans, slowing research, and depriving Americans of their ability to use marijuana for medical or other purposes," the senators wrote.