In a softening of its position, the ASTI has agreed to open "contacts" with the Department of Education over the contentious issue of payment for supervision and substitution.
Yesterday, the Department and the three teacher unions set the end of September as the deadline for agreement on the issue.
Until now, the ASTI had been refusing to take part in any discussions until its 30 per cent pay claim is settled.
At a meeting with Department officials yesterday, the ASTI reversed its policy and agreed to open contacts.
Already five meetings have taken place between the Department and the other teacher unions - the INTO and the TUI - and the school management bodies.
The TUI general secretary, Mr Jim Dorney, said it was now time for the Department to make a "realistic offer", as discussions had been going since April.
At present, teachers are not paid for supervision and substitution. Most perform the duties on a voluntary basis.
However, problems with this informal arrangement were highlighted during the ASTI dispute when schools had to close after teachers withdrew from this work.
The TUI is seeking an allowance of about £2,200 for supervision and substitution. It also wants the Department to recognise the principle that these duties are essentially overtime duties by teachers and should not form any part of their contract of employment.
The INTO wants teachers to be freed from any obligation to perform lunchtime supervision and it wants full cover for all teachers who are absent. It will, however, examine any offer made by the Department.
ASTI has threatened to impose a policy of non-co-operation with extra-curricular activities in the autumn unless its demand for a 30 per cent pay rise is met. But the union must ballot members before deciding on its next move.
An ASTI spokeswoman said last night: "A meeting was held between the Department of Education and representatives of the teacher unions and school management bodies today.
"The meeting dealt with a range of issues in relation to the start of the school year including the establishment of new posts of programme co-ordinators, a review of the posts of responsibility system, the ending of CES schemes in schools and supervision/substitution.
"In relation to the latter issue, it was agreed that contact will continue between the parties in an effort to find a solution by the end of September."