Members of the Transport Workers Union Local 100 have until tomorrow to vote on a three-year contract that, while likely to be approved, has deepened a rupture between union leaders and a small but vocal faction of dissidents.

Union ratification of the pact would end a bitter confrontation with the Metropolitan Transportation Authority that peaked with a three-day transit strike last month. The union’s executive board approved the deal, 37-4, but leaders of the opposition have campaigned aggressively in subway stations and at union meetings across the city against a deal they call the “mother of all givebacks.”

“Across the board, there’s strong animosity against it,” a union vice president, John Mooney, said yesterday.

Mr. Mooney and another opposition member of the executive board, Marty Goodman, also railed against a memo sent last week to all union officers by the president, Roger Toussaint. The two-sentence directive, dated January 9, threatens to dock the pay of any officer campaigning against the deal. “Any union paid officer who wishes to campaign against the proposed contract may do so only on his/her own time and/or on leave,” the memo reads.

The union said the memo is the same as one sent out during voting for the last transit contract in 2002, but Mr. Mooney said it was “an attempt to silence the opposition.”

He ignored the directive, and said he spent part of his shift yesterday campaigning in the Chambers Street subway station.

“If he’s going to withhold my pay, he’s going to withhold my pay,” Mr. Mooney said. “To me, it’s nothing new.”

A union spokesman declined to comment yesterday on the dissident movement, but said the union is “confident that the contract would be approved.”

When the dissidents held a news conference earlier this month to protest the proposed contract, Mr. Toussaint referred to them as “a few disruptive individuals” who “worked hand-in-hand with management all along.”

Union opponents of the deal say the 10.5% salary increase over three years is “inadequate” and have denounced terms that call for transit workers to pay a portion – 1.5% – of their wages toward health benefits for the first time.

Still, transit workers have not rejected a contract proposal since 1992, and neither Mr. Goodman nor Mr. Mooney would predict an outcome. “It should be a close one,” Mr. Mooney said.

The union has hired the American Arbitration Association to run the voting, which for the first time will be conducted by phone or via the Internet, instead of by mail. Company officials were not available to comment yesterday, and it is unclear how many of the 33,700 union members have voted. If the union ratifies the contract, the MTA board will vote on it January 25.

Meanwhile, a state Supreme Court judge in Brooklyn yesterday postponed a scheduled court appearance tomorrow by union leaders, including Mr. Toussaint, to deal with issues related to the illegal transit strike. Mr. Toussaint could face jail time or a stiff fine for violating a court order not to strike.