MIAMI BEACH, Fla. (AP) _ Delegates at the National Education Association's annual convention passed a resolution Friday that left it just shy of outright opposition to President Bush's conservative U.S. Supreme Court nominee.

The resolution expressed the union's ''grave concern'' over Clarence Thomas' conservative positions on affirmative action, ''reproductive freedom,'' and the minimum wage.

The measure, passed overwhelmingly in a voice vote by the 8,100 teacher- delegates, instructed their union to monitor the confirmation process. It also said the union would press for the nomination of a new candidate if it was determined that Thomas's positions are unacceptable.

''We're telling the NEA that if things don't change regarding what Thomas stands for, that it should work against his nomination,'' said Phil Rumore, president of the Buffalo (N.Y.) Teachers Federation, who wrote the resolution.

Bob Chanin, the NEA's attorney, said the resolution ''simply gives the NEA the flexibility to determine the best strategy to deal with the nomination.''

During the floor discussion, Chanin said the NEA had investigated Thomas when he was nominated to the Washington, D.C., Circuit Court of Appeals.

''We find the positions he has taken to be unacceptable to us,'' Chanin said. ''We find very little to be encouraged about him.''