St. Paul teachers will strike on Tuesday if a new contract is not settled in the coming days, the union announced Wednesday night.

When members of the St. Paul Federation of Teachers voted last week to authorize a strike, Feb. 13 had been mentioned as a potential date for a walkout.

The union and the school district have been in mediation this week and are expected to continue talks through the weekend.

In its announcement Wednesday, the union said its efforts to reduce class sizes, increase support staff positions and expand new approaches to discipline have failed to win agreement with the district.

For months, the district has said it aims to limit the costs of the new teacher contract to about $2.07 million — this after several years of budget cuts and enrollment declines.

According to district estimates, the total cost of the union’s proposals is $159 million.

The district has announced that all classes, including preschool and K-12, will be canceled if a strike occurs. After-school activities and athletic events could be in jeopardy, along with the ability of a high school senior to lock in the necessary credit hours to graduate.

The union also said its members began planning Safe Sites to serve students in the event schools are not available. “The goal is to make sure that students have safe, warm, and appropriate alternatives if schools are closed,” the statement said.