U.S. Sen. John Kerry, D-Mass., didn’t mince words Thursday in calling for the repeal of the long-standing ban on gay men donating blood.

“Not a single piece of scientific evidence supports the ban,” Kerry said  in Bay Windows, a New England-based gay and lesbian newspaper.

A letter to the FDA — spearheaded by Kerry and signed by 20 other Senate Democrats — is more guarded, calling for the administration to review — and modify, if appropriate — the long-standing prohibition.

“With hospitals and emergency rooms across the country in constant and urgent need of blood products, we believe certain blood donor deferral policies should be reviewed and appropriately modified and modernized while ensuring the blood supply meets the highest possible standards that we all expect in America,” the lawmakers write.

Still, they also seem confident that such a review would lead to the repeal of the blanket ban that they’re clearly advocating.

The safety, availability, and integrity of our nation’s blood supply are vital.  For these reasons, we agree with the American Red Cross, America’s Blood Centers, AABB, and others that the time has come for the FDA to modify the lifetime deferral for [gay men] to be consistent with sensible health and safety policy and with FDA deferral guidelines for high-risk heterosexual behavior.  We request that you initiate a review of the lifetime deferral requirement for men who have sex with men wishing to donate blood and that you reexamine the deferral criteria for all blood donors to ensure all high-risk behaviors are appropriately addressed.

Aside from Kerry, the letter was also signed by Democratic Sens. Kirstin Gillibrand (N.Y.), Dick Durbin (Ill.), Daniel Akaka (Hawaii), Sheldon Whitehouse (R.I.), Sherrod Brown (Ohio), Frank Lautenberg (N.J.), Bob Casey (Pa.), Bernie Sanders (Vt.),  Russ Feingold (Wis.), Mark Udall (Colo.), Al Franken (Minn.), Maria Cantwell (Wash.), Carl Levin (Mich.), Tom Harkin (Ohio), Mark Begich (Alaska), Roland Burris (Ill.) and Michael Bennet (Colo.).