Teachers and lecturers are being urged to vote to strike against changes to their pension.
The Educational Institute of Scotland (EIS), which represents 80% of teachers and lecturers, has opened a consultative ballot. Members will have three weeks to cast their vote.
The union has been negotiating with the Scottish Government to formulate a new pension agreement.
EIS general secretary Larry Flanagan said "little progress" has been made.
"While we continue to hope for a negotiated agreement, we will also be ready to continue the fight for a fair deal by the use of further industrial action if required," he said.
"I would urge all eligible EIS members to use their vote in this important ballot and to vote yes for industrial action to send a strong message to the Scottish Government."
Changes to pension arrangements will mean teachers could be made to work beyond 65.
"The EIS rejects completely the possibility that teachers should be forced to work until 68, or even later, in order to access decent pensions," Mr Flanagan said.
"Too many teachers already retire into ill-health for us to contemplate such an extension to what is an extremely stressful job."