Teachers in Oakland, California, are preparing to strike for a third day after negotiations with the school district broke down over the weekend.

Oakland Unified says in a statement that talks ended Sunday with no resolution on issues including salary and class sizes.

The district urged the Oakland Education Association to return to the table as soon as possible.

The union, meanwhile, vows that teachers will walk picket lines again starting at 6:30 a.m. Monday.

Oakland's 3,000 educators went on strike last week, picketing Thursday and Friday outside many of the city's 86 schools.

The teachers are asking for a 12 percent retroactive raise covering 2017 to 2020 to compensate for what they say are among the lowest salaries for public school teachers in the expensive San Francisco Bay Area.