Allina Health and the union for its 4,800 Twin Cities nurses detailed separate plans Sunday for taking care of patients during what could be a prolonged and painful nursing strike — despite the two sides coming closer to a deal in marathon negotiations this weekend.

The open-ended strike started at 7 a.m. at United Hospital in St. Paul, Mercy Hospital in Coon Rapids, Unity Hospital in Fridley, the Phillips Eye Institute in Minneapolis, and Abbott Northwestern. The walkout occurred despite 22-hours of talks on Friday and early Saturday that brought the sides as close to a deal as they have been in seven months of failed talks.

The 1,500 temporary nurses recruited from across the country should be enough to maintain normal operations at the five Allina hospitals under strike, said chief executive Penny Wheeler, because the replacements will work full-time, while two-thirds of the regulars are part-time.

As many as 350 regular nurses also have indicated they will cross the picket lines, she said, which doubles the number who did so during a one-week nursing strike in late June.

“We feel like we can staff this as long as we need to,” said Wheeler, adding that “patients should access all of our hospitals as they would normally.”

Meanwhile, the Minnesota Nurses Association, the union representing the nurses, said it had created a patient protection task force that would send striking nurses to work at the hospitals in emergencies.

“Nurses care for their patients, even beyond the bedside,” said Angela Becchetti, a nurse at Abbott Northwestern Hospital in Minneapolis and a union negotiator. “If Allina calls us, we would come back in to deal with medical emergencies.”

Talks have centered on Allina’s demand to terminate four union-backed health plans, which Allina officials have criticized as expensive and lacking in cost controls to prevent overuse of costly medical services, and to switch nurses to its corporate plans.

The union has defended its health plans as essential benefits for nurses with unusually high risks of workplace-related illnesses and injuries compared to other workers.

But both sides moved far off their initial positions during the weekend negotiations, which involved federal mediators.

Allina officials said they were willing to retain two of the union’s plans through 2019, to allow new nurses to choose the union plans through 2017, and to pay a proportionate amount of the cost increases of the plans through 2018. In the final year, it wanted to cap how much it paid for cost increases and make the nurses pay the rest.

“It seems unfair, quite frankly, to have those costs ride on the backs of our [other] employees and our communities,” Wheeler said.

The union’s final offer would have dissolved all four of the union health plans by 2020 if Allina agreed to limit the percentage of premiums nurses would be required to pay on the corporate plans. Allina also would have needed to gain the union’s consent before making changes to its corporate plans during the three-year contract that would have significantly altered their benefit value.

Valerie Johnson, an Abbott mental health nurse on the bargaining committee, was more worried about how nurses would react to this final proposal — which sacrificed the union health plans but gave the union authority over the value of the corporate plans.

“Then [Allina] said no,” she said. “We were shocked.”

Allina spokesman David Kanihan said the union in its final offer asked for too much control over the cost and benefit levels of the corporate plans, which also cover thousands of nonunion workers.

No further negotiating sessions are scheduled.