ST. PAUL, Minn. - Thousands of nurses at 14 Twin Cities hospitals voted overwhelmingly Wednesday to reject contract proposals and authorize a strike as early as next month in a dispute over pension benefits and staffing levels.

Minnesota Nursing Association spokesman John Nemo said more than 90 percent of the 9,000 nurses voting Wednesday backed a walkout, which the union says would be the largest nurses' strike in U.S. history.

The union said it would limit a strike to one day. Nemo said the date hasn't been picked, but it won't be until after the current contract expires on May 31.

"It's going to have the maximum impact on the employer, but cause the minimum amount of pain to the patients," Nemo said.

Maureen Schriner, a spokeswoman for six Twin Cities hospitals that are negotiating as a group, said they are preparing for a walkout by lining up temporary nurses and reducing the number of patients they'll have on strike days.

Several nurses said they hoped their vote would lead to more negotiations between the hospitals and the union.

"We want to be there for the kids," said Sandy Drummer, 61, a nurse at Children's Hospital in Minneapolis. "I don't want the kids to suffer for that, but they are going to suffer now or suffer later if we give in to (the hospitals') demands."

The hospitals want the ability to reduce nursing staff to levels that the union considers unsafe for patients. The hospitals say cuts can be made safely thanks to technology and procedural changes, but many nurses disagree.

"Technology does not replace nurses," said David Olson, 49, a nurse in the emergency department at Abbott Northwestern Hospital in Minneapolis who voted to authorize a strike. "It just doesn't happen." Nemo said the hospitals also want to cut pension contributions by a third.

Schriner said the hospitals want flexibility to respond to the recession and to changes in the regulatory environment, patient expectations and patient populations.

Nemo said the contract would allow the hospitals to move nurses from department to department to respond to patient demand. Nemo said nurses object to that because it could force them to work in areas they are not trained for.

Schriner rejected the idea that hospitals would move nurses into unfamiliar areas, saying doing so would be unsafe.

Some 12,000 nurses were eligible to vote on two proposals, one for a pension contract and one for a three-year labor contract. The union recommended "no" votes on both. A "no" vote also authorized a strike.

Schriner said the contract offer included small pay increases for all nurses, who earn an average of $79,000 a year. It also included pay raises with seniority gains and still permits nurses to work part-time while getting full-time benefits.

"This contract does not represent a major change," she said.

While a strike would affect thousands of patients, it wouldn't affect two of the largest Twin Cities hospitals, Hennepin County Medical Center in Minneapolis and Regions Hospital in St. Paul, nor two large suburban hospitals in Maple Grove Hospital and Woodwinds in Woodbury. Those hospitals don't have union nurses or a contract up for renewal.

Labor disputes between hospitals and their nurses aren't new in Minnesota. In 2001, about 1,350 nurses walked off the job at two Fairview hospitals and in 1984, 6,000 nurses struck the hospitals group for five weeks in what was then the nation's largest nurses strike.