Here we go again.

After putting New Yorkers through a crippling three-day strike last month, city transit workers have dropped another bombshell - rejecting a tentative contract by a margin thinner than a MetroCard.

After more than 22,000 votes were finally counted yesterday, the three-year offer went down to defeat by seven votes, 11,234 to 11,227.

While the shocking rejection doesn't mean another strike is imminent, it did expose bitter divisions in the Transport Workers Union Local 100, as negotiators from both sides head back to the bargaining table.

A clearly disappointed and somber Local 100 President Roger Toussaint announced the results at the office of the local's public relations firm in Manhattan, not the West Side union hall.

Flanked by his two top deputies, Toussaint read a brief statement that blamed a number of forces for the defeat - everyone from Gov. Pataki, who had criticized a key provision of the now-dead deal, to union dissidents whom Toussaint claimed waged a campaign of lies.

"We believe this result is a by-product of a number of negative and inappropriate interferences," Toussaint said.

Pataki and Mayor Bloomberg later urged both sides to move quickly and it appeared they would.

"We go back to the drawing board," Toussaint said.

But Metropolitan Transportation Authority Chairman Peter Kalikow said that although his negotiators were willing to talk, the agency will take steps next week toward binding arbitration.

The MTA will file a request with the state Public Employment Relations Board "in order to ensure a timely resolution of this matter for the sake of all New Yorkers," Kalikow said.

The rejected 37-month pact would have given the 33,700 TWU workers pay hikes totaling 10.5% and Martin Luther King Day as a new holiday. It would keep the retirement age at 55, and called for thousands of dollars in pension refunds for many workers.

But the deal also called for significant givebacks, including the first-ever worker contributions toward health-care insurance - a make-or-break issue for some who opposed the contract.

While that contribution was a modest 1.5% of workers earnings, many clearly felt the concession would have set a precedent where management would continue to take bigger and bigger bites out their paychecks.

"It's a moral victory for transit workers," said union official John Samuelsen, a former ally of Toussaint's who campaigned against the contract. "The notion that we should no longer have unpaid health care has been defeated."

The health-care contribution - coupled with the Taylor Law fines workers face for their strike - would have wiped out any wage gains in the first year, opponents noted.

They also pointed out that the pact would move the contract's expiration date from mid-December into mid-January, out of the holiday shopping season. That would weaken the bargaining power of a union that has walked off the job three times since the 1960s.

"We've all got families to feed and rent to pay," local vice president Marty Goodman said. "We're not selling house and home for a crummy contract like this one."

Toussaint led his members out on strike on Dec. 20, stranding millions of riders and costing the city and businesses an estimated $1 billion. They returned to work after three days on the picket lines. State mediators helped broker a tentative deal.

Mediators stand ready to help again, PERB Executive Director James Edgar said.

Toussaint did not take questions after his brief press conference; some of the dissidents, who stayed longer to address the media, dismissed talk of another strike.

Gene Russianoff of the Straphangers Campaign agreed that another strike wasn't in the cards.

"Our advice to riders for now is simple: Take a breath and await developments," he said.