New York University said yesterday it would not renegotiate a contract with its teaching and research assistants. By breaking off relations with the United Auto Workers, the union that represents about 1,000 graduate students at the school, NYU set the stage for what could be a disruptive strike.

NYU, for more than three years, has been the only private university in America with unionized graduate students. But when the National Labor Relations Board ruled last July that graduate students are not employees, it seemed only a matter of time before NYU unshackled itself from the graduate assistants’ contract.

In a preemptive move to soften the blow of its decision, the university also said yesterday that it would increase annual stipends for teaching assistants by $1,000 in each of the next three years, raising the minimum base stipend for doctoral students to $21,000 from $18,000.

That proposed increase largely hews to the terms of the graduate students’ contract, which expires August 31. Ratified in 2002, the contract guaranteed $1,000 annual increases in stipends. NYU also said it would continue to pay 100% of the health-insurance premiums of the graduate assistants.

Those terms did little to mollify officials at the Local 2110 of the UAW, which will soon lose the dues it collected from NYU graduate students.

“I’m disgusted. I’m thoroughly disgusted with NYU’s administration,” Local 2110’s president, Maida Rosenstein, said. “The first contract has been very good for the university’s workers. In doing this, they’re adopting the worst kind of union-busting, corporate ideology.”

Mr. Beckman said he could not immediately provide figures on the percentage of courses at NYU taught by graduate students. Like its peer universities, NYU has increasingly relied on graduate students to carry teaching loads. While NYU sees the work as an important part of the graduate students’ educational experience, the union says the university is exploiting cheap labor.

With their organizing position greatly weakened, NYU’s teaching and research assistants are left with few options and face the same uphill battle waged by their counterparts at Columbia University. The most obvious tactic would be to organize a strike of graduate assistants, which could lead to course cancellations, missed exams, and other academic disruptions.

Strikes at Columbia, one last spring that lasted four weeks and the other this spring lasting one week, caused some headaches for the Ivy League university but did not soften the administration’s resistance to recognizing a union of graduate students.

Mr. Beckman at NYU said the school factored the consequences of a possible strike into its decision-making.

“Obviously, we are aware of the prospect of labor actions, and we will take what we deem are the appropriate steps,” he said.

In a 3,500-word memo explaining its decision, NYU said the primary point of contention involved its concerns over grievances pursued by the union. The memo accused the union of undermining the “academic management rights” of NYU’s faculty by challenging how teachers are categorized. Several of the disagreements have involved the union’s demands, pursued to arbitration, that teachers be hired as graduate assistants rather than as adjuncts.

Ms. Rosenstein said the graduate students’ union has never filed a grievance asserting that it had the power to determine who teaches a course. She also said the union told the university it would “withdraw any grievances that were an obstacle to bargaining.”

“The union had repeatedly asked to meet with them over this issue,” she said. “And they refused to meet.”

The NYU memo said the very fact that the union filed the grievances under the current contract destroyed the university’s confidence in the possibility of coming up with new language that would protect the faculty’s prerogatives.

NYU began negotiating with the union soon after the labor board, in November 2000 – it was then dominated by Democrats – upheld a decision, made by a regional labor board director, that teaching and research assistants at NYU are primarily employees, and thus are entitled to rights to organize.

Last year, the board, with a Republican majority, took on an almost identical case involving Brown University’s graduate assistants and overturned its earlier decision. The board, in a 3-2 vote, concluded that graduate assistants are “first and foremost” students, noting that their status as assistants is contingent on their academic enrollment. The majority opinion said the board feared the “collective-bargaining process will be detrimental to the educational process.”

Barely a year after the board’s first ruling, NYU signed a contract with the graduate students’ union. Before the contract, the average stipend for graduate assistants at NYU was $12,000, according to the union.