House DFL backers of getting medical marijuana to critically ill children and adults say they have reached a compromise that could conclude what has been one of the this year's most contentious issues.

The deal, announced by House Speaker Paul Thissen, Majority Leader Erin Murphy and Rep. Carly Melin on Thursday, would create clinical trials of medical marijuana for the severely ill. If the medical researchers cannot obtain marijuana for the trial -- and they may not be able to because marijuana is a federally illegal substance -- the proposal would include "the option of a state-based manufacture of medication" for the trial.

The proposal closely follows a compromise DFL Gov. Mark Dayton came up with, except it adds in the possibility of state manufacture "if no federal clinical trial is approved." The plan would also add vaporization of marijuana for trial participants.

Thursday afternoon, Dayton said he was unsure whether he could support the new proposal.

"The bill places heavy new responsibilities on the Minnesota Department of Health, and I have asked Commissioner Ehlinger to assess the costs of its implementation and its practicability. I also want legal counsel to assess the potential liability to the State from sponsoring such trials," he said in a statement. "I will need that information before making any decision."

The House plan would stop well short of what some advocates had wanted.

"There will be no grow-your-own dispensaries and no smoking of marijuana permitted," under the plan, a news release said.

"All along, our goal has been a compromise that provides needed medicine to children and Minnesotans who need it while responding to concerns from law enforcement and the health community," Thissen, DFL-Minneapolis, said in a statement.

The House DFLers said that law enforcement, which had strenuously opposed more expansive medical marijuana proposals, "has signaled they do not oppose the legislation."

The Minnesota Senate has been moving on a separate, broader front to legalize medical marijuana.

Sen. Scott Dibble, DFL-Minneapolis, said he plans to proceed through the process with his bill, despite the House plan. Dibble said the Senate measure, which he is sponsoring, has enough support in the Senate to pass.

As House DFLers were unveiling their proposal, Sen. Branden Petersen, R-Andover, made clear on Twitter that the House plan does not go far enough for him.

Heather Azzi, political director of pro-medical marijuana Minnesotans for Compassionate Care, said her group does not support the House proposal either. She called it unworkable.

Dayton has said he stands with law enforcement on the issue but has also indicated some openness to discussions over medical marijuana.

You can read the entire proposal here.

Patrick Condon contributed to this post.

Photo: Thursday's announcement of a deal on medical marijuana/source: Matt Gillmer, Star Tribune

Updated to reflect reaction from backers of more expansive medical marijuana proposals and from Gov. Mark Dayton.