Two Democratic senators and a possible Republican presidential candidate joined forces Tuesday to push a bill to remove federal prohibitions on medical marijuana in 23 states where it's already legal.

Republican Sen. Rand Paul of Kentucky and Democrats Kirsten Gillibrand of New York and Cory Booker of New Jersey said their unusual coalition is a sign of growing acceptance of medical marijuana.

The lawmakers introduced a bill intended to eliminate uncertainty surrounding marijuana use in states and the District of Columbia that allow it for medicinal purposes. The bill also would allow doctors at veterans' hospitals to prescribe pot for medical purposes and allow banks to provide checking accounts and other financial services to marijuana dispensaries.

"This bill we are introducing seeks to right decades of wrong and end unnecessary marijuana laws," Booker said at a Capitol news conference, where lawmakers were joined by veterans and other patients who use marijuana to relieve pain or suffering. All said they fear prosecution if they move to a different state or if the federal government decides to crack down on medical marijuana use.

"Our federal government has long overstepped the boundaries of common sense, fiscal prudence and compassion with its marijuana laws. These laws must change," Booker said.

"Otherwise law-abiding Americans -- bankers, business people, veterans and families-- are fearful of unnecessary, expensive, life-disrupting investigations and prosecutions," Booker said. "Today we join together to say enough is enough."

Paul, a doctor who is considering a bid for president, said Americans "are changing our opinions on restricting people's choices as far as medical treatments" and said the bill would allow patients with incurable diseases to receive needed relief.

"There is every reason to try to give more ease to people in the states who want this -- more freedom for states and individuals," Paul said.

The measure also would reclassify marijuana as a so-called Schedule 2 drug, rather than Schedule 1 as currently listed. The shift would recognize "accepted medical use" of marijuana and make it easier for doctors to prescribe it. The change also would make it easier for universities to conduct research on medical uses for marijuana without fear of prosecution.

Gillibrand said Congress needs to catch up with the nearly two dozen states that have recognized the value of medical marijuana to treat diseases ranging from multiple sclerosis to cancer to epilepsy and seizure disorders.

"This is clearly a case of ideology getting in the way of scientific progress," she said.

The three senators said they hope to bring the bill to a floor vote this year, but acknowledge it is likely to face strong opposition.

Gillibrand said she would personally lobby her colleagues, adding: "I dare any senator to speak to the patients here and say they don't deserve the medicine their doctors have prescribed," she said.

Marijuana legislation also has been introduced in the House.