Nurses at 12 of 13 Twin Cities hospitals voted Thursday to reject a contract offer and authorize a strike.

The Minnesota Nurses Association, which represents 7,900 metro-area registered nurses, said it will file an intent to strike notice Monday. A walkout could occur as soon as June 1.

"With an overwhelming 80 percent voter turnout, the results send a message of solidarity and commitment to improving working conditions for nurses and ensuring safe patient care, the union said in a statement issued when the votes were counted," just after midnight.

Only nurses at North Memorial Medical Center approved their contract. Management's offer of a 19.1 percent wage increase over three years exceeded the 18 percent offered by the other hospitals. North Memorial also said it would match the final settlement with the other hospitals if it turned out to be higher.

Negotiators for both the MNA and the hospitals said they expected talks to resume in an effort to avoid a strike.

If a walkout occurs, the following hospitals would be affected: Abbott Northwestern; Phillips Eye Institute; Children's Health Care (Minneapolis and St. Paul); Fairview (Southdale and Riverside Campus); HealthEast (St. Joseph's, Bethesda, St. John's); Mercy Hospital; Methodist; United.