DETROIT — The longest strike against General Motors in half a century isn’t over yet.

Leaders of union locals voted Thursday to approve a tentative contract agreement with the automaker, but said the strike — already a month old — would continue until workers voted to ratify the deal.

After meeting for more than five hours in Detroit, the group said voting by the 49,000 members of the United Automobile Workers at G.M. plants would begin on Saturday and be completed within a week.

The union leadership did not comment after the meeting, which brought together nearly 200 U.A.W. representatives, and it was not clear whether there had been dissension in the room. But it will now be up to those representatives to sell the agreement to members.

According to a summary posted online by the union, the four-year deal includes wage increases, and a formula for allowing temporary workers to become full-time employees. It also provides for workers to reach the same top wage regardless of when they were hired, overhauling a dual-scale system that has produced wide pay disparities.