Teachers in England will vote on whether or not to go on strike if the government stands by its pay offer for the next school year.
The National Education Union (NEU), England's largest teaching union, says it will hold a formal ballot if the offer remains "unacceptable", or if no extra funding is announced.
The government has recommended a 2.8% pay rise for teachers and expects most schools will need to make "efficiencies" to fund it.
Education Secretary Bridget Phillipson said "any move towards industrial action by teaching unions would be indefensible".