MINNEAPOLIS — More than 12,000 nurses this morning launched a one-day strike at 14 Minnesota hospitals in a dispute over staffing levels and pension benefits.

Nurses wearing red T-shirts and carrying signs began walking the picket lines at 7 a.m. At Abbott Northwestern near downtown Minneapolis, several hundred nurses were serenaded by another nurse playing "Amazing Grace" on bagpipes.

Sue Stamness, a nurse in the cardiology unit for 24 years, said the nurses are striking because they are concerned that patient safety is at risk due to thin staffing.

Hospitals say patient safety is a top priority. They have arranged for replacements for the nurses and the immediate effect of the strike is expected to be minimal.