The Pittsburgh Public Schools and its teachers union bargained for about 51/2 hours yesterday and will meet again tomorrow and Friday.

Pittsburgh Federation of Teachers President John Tarka declined to say whether progress had been made. District officials did not immediately respond to a request for comment.

The PFT represents about 3,500 teachers, other professionals, aides and technical-clerical workers who have been without contracts since June 30. Union members have authorized their leadership to call a strike if necessary.