Teachers in England have said they would be willing to strike over the government's proposed 2.8% pay rise this year.
The offer was rejected by 93.7% of members of the National Education Union (NEU), England's largest teaching union, who took part in an informal ballot.
And 83.4% indicated they would be willing to strike in the vote, which aimed to gauge teachers' mood.
Education Secretary Bridget Phillipson said "any move towards industrial action by teaching unions would be indefensible".
The vote does not mean teachers are about to strike.
They have to support industrial action in a formal ballot before that can happen, and enough of them have to vote.
A vote on the next steps will take place at the annual conference of the NEU in Harrogate next week.
Any formal ballot would be likely to take place in summer.
"There's increasing demands on teachers now, more than there ever has been," he said.
"That is beyond planning and marking. There's now increasing demand on schools to support the most vulnerable students and families."
The results of the NEU's indicative ballot, which ran from 1 March until Friday, showed:
A total of 134,487 teachers voted, representing less than half (47.2%) of eligible members.
NEU general secretary Daniel Kebede said the government "must listen to our profession and change course on teacher pay".
"It must recognise the dire state of school funding and invest in education, to give the next generation the best chance possible in life," he said.
Ms Phillipson said: "With school staff, parents and young people working so hard to turn the tide on school attendance, any move towards industrial action by teaching unions would be indefensible.
"Following a 5.5% pay award in a hugely challenging fiscal context, I would urge NEU to put children first."
Additional reporting by Branwen Jeffreys and Hope Rhodes.