As buses began to warm up Thursday night and workers went about the complex task of bringing the 660-mile subway system back to life — inspecting tracks, testing brakes, restoring power — the mood could not have been more different than it was 24 hours earlier, when many signs suggested the strike could be a long one.

On Wednesday, Roger Toussaint, the president of Local 100 of the Transport Workers Union, had traded barbs with Bloomberg and Gov. George E. Pataki from afar as all three drew what seemed to be deeper lines in the sand. Toussaint said he would agree to talk only if the Metropolitan Transportation Authority would remove the nettlesome question of pensions from the negotiations; Pataki said no talks could take place until the strike ended.

But behind the scenes, both sides were meeting with state mediators. At 2 a.m. Thursday, Toussaint arrived at the Grand Hyatt hotel, where negotiations had been taking place, suggesting major progress was occurring.

Three state mediators conducted an 11 a.m. news conference that gave New Yorkers their first reasons for hope in days.

The mediators said the union's leadership had agreed to send strikers back to work after accepting the preliminary framework in which the transportation authority hinted it might take off the table the main obstacle to a settlement: its demands that future workers pay 6 percent of their wages toward their pensions.

As part of that framework, the union agreed to negotiate over having transit workers pay more for their health coverage to offset the money the authority would lose by relinquishing its pension proposals.

The mediators, led by Richard A. Curreri, director of conciliation for the New York State Public Employment Relations Board, said they expected the two sides to engage in intense negotiations to reach an overall settlement, hopefully in the next few days.

"An agreement remains out of the parties' reach at this time," the three mediators said in a statement. "It is clear to us, however, that both parties have a genuine desire to resolve their differences. In the best interests of the public, which both parties serve, we have suggested, and they have agreed, to resume negotiations while the TWU takes steps toward returning its membership to work." "The MTA," the mediators continued, "has informed us that it has not withdrawn its pension proposals, but nevertheless is willing to discuss whether adequate savings may be found in the area of health costs."

Two officials close to the talks, one on the authority's side and one on the union's, said the authority would soon take its pension demands off the table.