TORONTO - The union representing teaching assistants and other academic staff at Ontario's two largest universities warns a potential strike in the coming days could jeopardize the school year for thousands of students.

The Canadian Union of Public Employees says about 10,000 non-tenured academic staff at the University of Toronto and York University could walk off the job if they don't get a contract with a "modest" salary increase.

CUPE says the University of Toronto staff will be in a legal strike or lockout position on Thursday while those at York University will be in a legal strike or lockout position on March. 3.

CUPE says teaching assistants provide about 60 per cent of the undergrad instruction at U-of-T and York, but account for only 3.5-to-eight per cent of the universities' operating budgets.

Union president Fred Hahn says teaching assistants get paid $15,000 a year -- $8,000 below the poverty line -- and they must pay tuition on top of that.

He says they also need increased job security, noting many don't know from one semester to the next if they will have a job.