PROVIDENCE - The Senate easily overrode Gov. Donald L. Carcieri's veto of medical marijuana legislation Thursday, and House leaders promised to do so soon.

If House leaders are able to muster the votes needed to override Carcieri's veto, Rhode Island would become the 11th state in the country and third in New England to legalize marijuana use for patients with debilitating diseases. Vermont and Maine already have enacted medical marijuana laws.

The Senate voted 28-6 to override Carcieri's veto. They only needed a 60 percent margin, or 21 votes, for the override. All five of the chamber's Republicans changed their votes from the first Senate consideration of the bill to support Carcieri. The only Democrat to vote against overriding the veto was Sen. Marc Cote, D-Woonsocket.

"This is going to mean there will be another alternative for people," said Sen. Rhoda E. Perry, D-Providence, who sponsored the Senate version of the legislation. "They will no longer have to be as frightened of using marijuana for their pain."

Rep. Thomas C. Slater, D-Providence, who sponsored the House version, said that House leaders told him they would not override the governor's veto before this year's session ends, probably today or Tuesday, but promised to return in a few weeks to hold an override vote. The House approved the legislation by a 51-10 vote.

"I'm confident the votes are there to override," Slater said.

After Senate Minority Leader Dennis L. Algiere, R-Westerly, read part of the governor's veto message and urged senators not to override the veto, several Democrats argued that the legislation was aimed at showing compassion to those with serious medical problems.

"Put a human face on it," said Sen. Joseph M. Polisena, D-Johnston. "Think if someone you love was dying or was suffering. Would you go out and get them some marijuana? If you said you wouldn't, you're lying."

"If we can do anything to alleviate the pain or increase the appetite of someone ... let's do it. I have never seen anyone die of a marijuana overdose," said Sen. Michael J. Damiani, D-East Providence, who is a retired police officer.

The legislation would allow doctors to prescribe marijuana for patients with serious diseases including cancer, multiple sclerosis or AIDS.

Once the state Department of Health receives written notice from the doctor, it would issue photo identification cards to the patient and at least two caregivers, who would be able to assist the patient in procuring marijuana.

Authorized patients would be able to possess up to 2.5 ounces of "usable marijuana," which does not include stems and seeds, or grow up to 12 marijuana plants inside their homes.

If the law is approved, the Department of Health would have to issue a progress report on the law by January 2007. The law would expire June 30, 2007, unless the legislature acts to extend it.