Minneapolis teachers could go on strike as early as November 11.
The union filed the intent to strike notice on Friday, and strike would happen if no contract is reached during the ten-day cooling off period.
The two sides were back at the bargaining table last week after the union authorized a strike.
They met for more than 30 hours in a session that began on Wednesday, with no agreement.
"Our phone line is open, our email is open, our hearts are open, and our hope is open that there are people that are willing to actually come to the table and negotiate," said teachers union leader Marcia Howard
Nearly all who voted last weekend favored walking off the job.
At issue are wages and class sizes.
More talks are scheduled before the strike date.
"I would say that's purely up to our district leaders, what they come back with," said Catina Taylor, who leads education support personnel. "Sometimes, the bosses could be the best organizers."
School administrators say they want a contract that works within available resources.
It was just three years ago when Minneapolis teachers walked off the job for three weeks.