Four big Twin Cities safety-net hospitals signed onto a revamped state health care plan for vulnerable adults Thursday, ensuring that a program some feared would never get off the ground will start next month.

Human Services Commissioner Cal Ludeman said the hospitals together will care for about half the patients now covered by the General Assistance Medical Care program. That program covers more than 30,000 poor adults a month, including the homeless, mentally ill and drug-dependent.

The hospitals are Hennepin County Medical Center, Regions Hospital, North Memorial Medical Center and University of Minnesota Medical Center, part of the Fairview system.

Democrats who run the Legislature and Republican Gov. Tim Pawlenty struck a deal two months ago to preserve the GAMC program by slashing payments to hospitals. But hospitals balked at the low reimbursements. Most refused to sign up, and Democrats have since soured on the plan.

Instead they have been pushing to buy into an early Medicaid expansion option under the federal health care overhaul, an approach Pawlenty has resisted because the state has to put up matching money. Thursday’s announcement seemed to put that option further out of reach.

"I don’t think it’s likely to happen on my watch," Ludeman said.

Ludeman said it would be disruptive to switch the patients to another program before mid-2011.

The four hospitals signed onto the deal struck in March. The new GAMC program aims to keep costs down by having hospitals manage care for the patients, slotting them into other subsidized programs when appropriate and trying to get them preventive care to head off expensive hospitalizations.

Rep. Erin Murphy, one of the lead Democratic negotiators, said she was pleased that four hospitals signed up but still worries about the patients who won’t be covered, particularly outside the Twin Cities. She said she hasn’t given up on the federal Medicaid expansion.

"We still have a gap to fill," she said.

GOP Rep. Jim Abeler of Anoka said the program is off to a good start. He supports the new approach of paying the hospitals a lump sum to care for the patients instead of reimbursing them for each procedure.

"Now we have a metro system that can work," he said. "Upon that we can build."

Hennepin County Medical Center spokesman Tom Hayes said the county and hospital boards approved the deal Thursday. He said the contract will limit the number of patients that the hospital must cover under the plan, reducing its financial risk.