The prognosis for a Minnesota House bill to legalize medical marijuana grew hazy Tuesday when its chief sponsor said negotiations with opponents have deadlocked.

“We had offered them a number of concessions,” Rep. Carly Melin, DFL-Hibbing, said in an interview. “They still rejected the proposal, so I just don’t know where to go from here.”

A House committee was scheduled to hear the bill Tuesday, but Melin postponed the hearing after negotiations with law enforcement groups who oppose the legislation failed to produce an agreement.

The groups fear the potential for abuse under the bill, and Gov. Mark Dayton has urged supporters to work out a compromise.

Although Dayton signaled Tuesday that there’s time to reach an agreement, House Speaker Paul Thissen, DFL-Minneapolis, said the issue could be dead.

“This session we have brought both sides on this issue together multiple times to see if there was a compromise that could be reached,” Thissen said in a statement. “It does not appear to me that a compromise is going to happen this session.”

Thissen has said it would be unlikely for the House to take up Melin’s bill on the floor without a compromise agreement.

With sponsors from the Democratic-Farmer-Labor and Republican parties, Melin’s bill would make marijuana available to people with conditions such as cancer, glaucoma and HIV/AIDS, so long as doctors certified patients might benefit.

Patients would apply to the Minnesota Department of Health for ID cards, which they would use at a network of dispensaries or “alternative treatment centers” across the state. Patients would receive 2.5 ounces of marijuana.

To address their law enforcement groups’ concerns, Melin said, she offered to drop provisions that would have allowed some patients to grow marijuana at home. She also offered to prohibit smoking the drug, while allowing use by vaporization.

But Dennis Flaherty, executive director of the Minnesota Police and Peace Officers Association, said the concessions didn’t go far enough.

Patients still would have been allowed to use marijuana for post-traumatic stress disorder and conditions that result in intractable pain — uses that have the “potential for abuse,” Flaherty said.

Law enforcement groups also wanted to limit use to marijuana derivatives in the form of pills, oils or vapors, Flaherty said, but not vaporization of marijuana leaves.

“The differences are so wide, I just don’t think in this short (legislative) session that we ever are going to be able to come to any comfort,” he said.

Supporters say the measure has popular support. The House’s health policy committee gave its endorsement last week after hearing emotional testimony from patients in support of the bill.

The hearing featured parents of children with seizure disorders who are exploring out-of-state options to obtain treatment with a liquid formulation of medical marijuana.

“I think it’s time for the public and patients to ask the governor to change his position, or to provide some movement,” Melin said.

“Of course, law enforcement would be opposed to medical marijuana,” she said. “Why would they support it?

“I think we need to open our minds a little bit and look at the other input besides just (law enforcement) in making this decision.”

The issue isn’t dead this year at the Capitol, said Heather Azzi, spokeswoman for Minnesotans for Compassionate Care, which has backed the bill.

“The governor has been letting law enforcement do his job on this issue for too long now,” Azzi wrote in an email.

In a statement, Dayton responded to Tuesday’s developments by saying: “The two months remaining in the legislative session provide ample time to negotiate medical marijuana legislation, which incorporates the legitimate concerns of not only law enforcement officers, but also many medical, mental health and other experts.”

Law enforcement groups support more research into the possibilities with medical marijuana, Flaherty said, because there likely are patients who could benefit. But, he said, legalization before such studies would send the wrong message.

During negotiations with bill supporters, law enforcement officials offered a narrow proposal that would have allowed use of marijuana derivatives with little or no THC — the chemical component of marijuana that gets people high, Flaherty said.

They also sought to limit patient access to those with AIDS, cancer, glaucoma and seizures, he added.

Law enforcement groups might not have supported the proposal, Flaherty said, but they might not have opposed it.

“We are concerned about the increased usage of marijuana by kids,” he said. “We look at it as a gateway drug. We look at it as a drug that is very addictive.”

The Minnesota Medical Association has not taken a position on the bill. But doctors also have called for more studies, even as some physicians say they support legalization of medical marijuana while others oppose it.

About 20 states allow patients to use medical marijuana. In almost all cases, legalization came from constitutional amendments, Melin said, rather than through legislative action.

But Melin said she doesn’t currently support the idea of asking voters to ratify a constitutional amendment.

“That’s not a route that I want to go,” she said. “Politicians should have the courage to take a vote on something. … I don’t know if there will be a constitutional amendment, but I’m not bringing one forward at this time.”

Christopher Snowbeck can be reached at csnowbeck@pioneerpress.com or 651-228-5479. Follow him at twitter.com/ chrissnowbeck.