ALBANY  Following in the footsteps of Connecticut's Legislature, New York State lawmakers are expected to approve legislation allowing the use of marijuana for medical purposes.

The Democrat-led Assembly could pass a medical marijuana bill as early as this week, according to the bill's main sponsor. The Republican-led Senate is expected to follow suit, lawmakers said.

It's not clear if Governor Spitzer would support the bill. As a candidate last year, Mr. Spitzer said he was opposed to the legalization of medical marijuana, but a spokeswoman for the governor indicated yesterday that he has not ruled out signing such a bill.

"We know that the issue is being discussed by the Legislature and a variety of proposals have been discussed," a spokeswoman for Mr. Spitzer, Christine Anderson, said via e-mail. "If they pass a bill, we'll obviously take a look at it."

Governor Rell of Connecticut, who is considering a medical marijuana bill that lawmakers sent to her desk earlier this month, has also given mixed signals about her position. She has said it's important to help seriously ill people alleviate their pain, but has expressed fear that legalizing the drug would undermine the message that recreational use of marijuana is dangerous.

New York would be the 13th state to approve a medical marijuana program and the fifth state to approve the use of the substance through legislative action. Eight states have permitted medical marijuana by voter referendum.

In 2005, New York lawmakers came close to approving a medical marijuana law. They backed off after the Supreme Court ruled that the federal government can prohibit doctors from prescribing the drug. Since the ruling, states have increasingly reasserted their right to permit use of the drug under certain conditions.

New York is moving closer to legalizing medical marijuana at a time when the movement appears to be gaining momentum.

In the last two months, in addition to the legislative action in Connecticut, New Mexico became the 12th state to legalize medical marijuana; Vermont lawmakers voted to broaden their program, and Rhode Island lawmakers passed a bill making the state's medical marijuana law permanent, and are expected to override Governor Carcieri's veto.

"The issue has just started to reach critical mass," a spokesman for the Marijuana Policy Project, Bruce Mirken, said. "There's a growing awareness among politicians that's it's not a scary issue."

The bill introduced in the Assembly is similar to Rhode Island's law. It would allow the possession of up to 2.5 ounces of marijuana and up to 12 plants by a certified patient or designated caregiver.

Patients would be barred from purchasing marijuana and smoking it in public places. A doctor could certify the use of marijuana for up to one-year intervals to a patient suffering from a life-threatening condition. The doctor could certify the drug only if he or she believed that it would be more effective than other drugs.

Critics of medical marijuana say the dangers of using the drug outweigh any medical benefits. Opponents also argue that there are available legal medicines that could offer similar relief. There is a fear among some critics that legalizing the drug would make it easily available to people who are not authorized to use it and would make the drug seem safe.

"I think it's wrong," the chairman of the Conservative Party of New York, Michael Long, said. "I don't think there's any way to keep track of what's going on. Who's to say that marijuana is not being picked up by teenagers in the house?"

Supporters contend that marijuana can offer relief to people suffering from cancer, glaucoma, AIDS, Crohn's disease, hepatitis-C, and multiple sclerosis. The prohibition, they say, hasn't stopped sick people from seeking the drug but has driven up the cost, meaning they have to spend hundreds of dollars to obtain just one ounce.

They also argue that the drug is especially beneficial to sick people who don't respond well to other medication and that smoking the plant is more effective than taking the synthetic and legal pill version made with THC, the psychoactive ingredient in marijuana.

"It's humane, and it's good medicine," a Democratic assemblyman of Manhattan who is the lead sponsor of the bill in the chamber, Richard Gottfried, said. "There are thousands of New Yorkers who suffer from serious medical conditions who could have a better quality and longer life."

A Senate Republican who in previous years has sponsored medical marijuana bills in the chamber, Vincent Leibell, said he's optimistic that the house would back a marijuana bill, although one with a different wording from the Assembly version.

"I believe there's support there," he said.

Mr. Leibell said it's likely that he would put forward a bill when the Assembly votes on its version. The Senate majority leader, Joseph Bruno, who is a survivor of prostate cancer, has said he supports legalizing marijuana.