10/14/2013 07:40 EDT | Updated 12/14/2013 05:12 EST

Threat of San Francisco Bay-area transit strike looms larger as agency sticks by final offer

OAKLAND, Calif. - The threat of a gridlock-inducing strike in the San Francisco Bay area looms larger as a regional transit agency and two of its largest unions remained without a deal hours before a midnight deadline.

The parties held talks Monday after the unions backed off a threatened strike deadline late Sunday and gave Bay Area Rapid Transit managers a 24-hour reprieve.

By late afternoon both sides appeared to remain firm in their positions.

BART's board president urged the unions to let its members vote on the agency's final offer that was presented Sunday.

A union leader urged BART to tweak its offer.

Pete Castelli of the Service Employees International Union Local 1021 said "it will take a hail Mary to prevent a strike" and that commuters should prepare for that possibility.