The liberal legislator and potential 2016 presidential candidate tweeted that the FDA must “have courage to set policies based on science” in order to “commit to building a bigger, safer blood supply through risk-based screenings.”

The policy, introduced Tuesday by FDA Commissioner Margaret Hamburg, would replace a 30-year-old ban on blood donations from gay and bisexual men with a new rule permitting donations from men who haven’t had sex with another man for at least a year.

( Also on POLITICO: Skip sex? FDA recommending new blood donation policy for gay men)

The lifetime ban dates from the early years of the AIDS crisis. “This recommended change is consistent with the recommendation of an independent expert advisory panel the HHS Advisory Committee on Blood and Tissue Safety and Availability,” Hamburg stated.

Earlier this month, Warren wrote a letter, along with Sen. Tammy Baldwin (D-Wis.), Sen. Tom Harkin (D-Iowa), Rep. Mike Quigley (D-Ill.) and Rep. Barbara Lee (D-Calif.), that was signed by 75 congressional colleagues and called for Health and Human Services Secretary Sylvia Mathews Burwell to end the “outdated MSM blood donation policy.”

It also criticized the proposed policy, stating that both the old and new policies are “discriminatory,” “unacceptable” and that “science has shown us that our current policy is not justified.”