BOSTON, June 11 -- The United Steelworkers said union members may vote June 24 on a labor contract proposed by Alcoa Inc., the largest U.S. aluminum maker.

Copies of the agreement will be printed and mailed to union members at Alcoa's U.S. plants tomorrow to review before the vote, Steelworkers official Gerald Dickey said today in an interview. The agreement would replace a contract that expired June 1.

Under the proposed agreement, the almost 6,000 workers at 11 plants across the U.S. would receive a 5 percent increase in wages phased in over the final two years of the four-year agreement, according to a summary posted on union Local 105's website. The workers will receive a $1,250 signing bonus if they approve the accord by June 30 and avert the first strike at the plants since 1986.

In the first two years of the agreement, the workers get lump-sum payments totaling $2,750 in lieu of wage increases, according to the summary of the proposed agreement. Weekly employee contributions for a family health plan would rise 47 percent to $47 in the fourth year from $32 a week in the first year, the summary shows.