The union representing Ontario's public high school teachers says it has suspended labour negotiations with the Ontario Public School Boards Association and the government management team.

In a memo sent out Tuesday, the Ontario Secondary School Teachers’ Federation said they have reached an “impasse” after 14 days at the central bargaining table and are temporarily walking away from negotiations to give the other side an opportunity to “reconsider their current bargaining positions.”

“Our negotiating team will remain ready to return to the table if and when OPSBA and the Government are ready to enter into serious discussions,” the memo said.

The union has threatened to withdraw services at seven school boards including Peel, Durham, Halton, Ottawa-Carleton, Waterloo, Rainbow and Lakehead.

High school teachers at the Durham District School Board have given legal strike notice and could walk off the job this Monday, April 20. A notice posted on the Peel District School Board's website says the earliest Peel high school teachers could legally go on strike is April 25.

Ontario's Education Minister Liz Sandals said the province is encouraging the union to resume negotiations.

"We really believe that if we all get to the table, the union, the boards, the government, if we are all at the table, that we can actually work together and negotiate a collective agreement," she told CP24 Wednesday.

Sandals would not comment on what issues are hampering talks, adding that she does not intend to "negotiate in the media."

Sandals said the province is taking the possible impending strike in Durham "very seriously."

"In the case of the Durham District School Board, they have given the legally required five-day strike notice for Monday, April 20 so we obviously take that very seriously and understand that of course that parents and students are concerned," she said.

"That’s why we are calling on everybody to come back to the table."

Michael Barrett, chair of the Durham District School Board, said that he believes the union will likely use local action in Durham as a way to apply pressure at the provincial bargaining table.

"Local negotiations are still going on at this point so they could be circumvented," he said Wednesday.

However Dave Barrowclough, the president of OSSTF District 13, Durham's local bargaining group, said the decision to walk away from the table at the provincial level will have no bearing on whether Durham high school teachers go on strike on Monday.

"Our strike here in Durham is based on local issues here at our local table," he said.

Barrowclough said they will be at the table negotiating throughout the weekend.

"I think we’ve got enough time. I know we’ve got the will to sit down because I certainly don’t have any interest in taking my members out," he said.

"We are just not seeing anything on the other side of the table at all. We are pretty frustrated on that front."

If an agreement is not reached by Monday, the Durham District School Board confirms it will close all high schools.

Board spokesperson Andrea Pidwerbecki told CTV News in a written statement that "contingency planning continues."

"We share students’ and families concerns and would also like to find a negotiated settlement with no interruption to the school year," she said.