With hundreds of city school bus drivers preparing to go on strike, Mayor Bill de Blasio is urging parents not to worry.

Teamsters Local 553 Union says 85 percent of its members at Jofaz Transportation and Y-and-M Transit voted to authorize a strike, which could begin as early as Tuesday. The union says it is pushing back against rising healthcare costs and reduced holiday time.

De Blasio says he is hopeful the bus companies and the union can strike a deal.

"We think there's a very high likelihood that this can be resolved by Monday and that is the last day currently that the workers would be on the job," the mayor said. "So we are very hopeful of resolution in time to keep the school buses running and not disrupt our kids getting to school."

De Blasio says that both companies serve around 12,000 public school kids, who are mostly in parts of Brooklyn, Queens and Staten Island.

The city says if a strike does take place, it will offer affected parents a choice of free Metrocards or paid car service for their kids.