A federal mediator has called Twin Cities hospitals and their nurses back to the negotiating table in a bid to head off what could be a costly and extended work stoppage.

Both sides said they have agreed to meet Thursday, though it remains unclear if that would lead to extended talks. The union voted Monday to authorize a strike.

"Our nurses look forward to returning to the bargaining table Thursday and are hopeful we can engage in meaningful negotiations with the Twin Cities Hospitals," the Minnesota Nurses Association said in a written statement.

"As we stated prior to this week's strike vote, we have given our unilateral commitment that we will not give a strike notice as long as productive negotiations are continuing," the union said.

Maureen Schriner, a spokeswoman for the hospitals, said she was encouraged by an offer from union negotiators last week to modify their contract proposal.

"Do we see the possibility of movement? Yes," she said, but added: "The concern the hospitals continue to have is that the union has been making moves to rush to another strike."

The nurses' one-day walkout on June 10 appeared to cause only modest disruptions to patient care, but an extended strike could inflict grave economic costs on both sides and create greater disruption in Twin Cities medical care.

The 12,000 nurses and 14 hospitals they work for are clashing over staffing, wages, work rules, pensions and health benefits. A central point of contention is the nurses' proposal for formal nurse-to-patient staffing ratios. The union says this would improve hospital safety and patient care. Hospital leaders say formal staffing ratios would greatly increase health care costs without any proven impact on patient care.

Negotiators last met on June 4, just after the nurses' contract expired May 31.

On Monday, the nurses voted to authorize an open-ended strike, upping the ante after their 24-hour strike failed to sway the hospitals.

The union would still need to give 10 days' notice of any strike.

More than 8,200 of 12,000 union nurses voted Monday, with 84 percent in favor of authorizing a strike.

The highest proportion of yes votes -- 90 percent -- came from United Hospital in St. Paul and the lowest -- 81 percent -- from Unity Hospital in Fridley.

Chen May Yee • 612-673-7434