The lack of early progress in negotiating sessions between Yale University and its union workers has raised the possibility of another strike like the one that disrupted the school three years ago, but both sides this week said they are still optimistic that they can reach an agreement.

"It's going slow. We're just starting to get into the meat of the issue," said Thomas V. Gaudioso, president of the 1100-member service and maintenance union, which is for the first time negotiating in conjunction with the clerical and technical workers' union.

"Progress has not been good," said Sheila W. Wellington, secretary of the university. But she added that "things continue to go acceptably" and that "we still remain cautiously optimistic."

"Everything is not carved in stone," Gaudioso said. "We're willing to discuss everything and try to find a middle ground." But on health and safety issues, he said, "we cannot accept a middle ground."

The unions are pursuing higher pay and more promotion and transfer opportunities, but according to Gaudioso, their most important concerns are job classification, health and safety.

The way a worker's job is classified is important because it determines his salary. The unions claim that some workers' classifications are too low for the work they do, said graduate student Leslie Frane, a member of the Yale Labor Support Group.

In addition, the unions claim that workers doing the same job at separate Yale facilities are receiving unequal pay because of their different classifications, Frane said.

The unions are concerned with health and safety issues because of a recent radiation spill and chemical explosion that damaged Yale laboratories, Gaudioso said.

Both sides said they will do their best to avoid a strike. The unions' deadline for a contract agreement is December I, but the unions' contracts will not expire until January 16.

"There's a very strong community sentiment against a strike," Wellington said. "I know the university is going to work very hard to avoid one," she said.

"We don't feel that every three years the whole community has to be disrupted," Gaudioso said. "We don't want to strike, obviously, but if we are left no other alternative, we will have to," he said.

The negotiations began more than two weeks ago. They are the first since the contract dispute in 1984, in which a full-scale strike left the campus without maintenance and service for ten weeks and forced students to fend for their own food.

Yale students, especially those who remember the last strike, have become involved in groups like the labor support group, which intends to mobilize the university community to put pressure on the administration.

"The crisis is now," said senior Abel Halpern, a member of the group. "We need to put the heat on the administration and let them know that we will not tolerate another strike," he said.

Between them, the two unions have gone on strike five times in the past 16 years, Gaudioso said.