A UNION representing some school leaders in Northern Ireland will not join the planned teachers strike next month.
The National Association of Head Teachers (NAHT) has written to its members telling them it "has decided not to call upon members to strike at this time".
But it says it "firmly and resolutely behind the strike action" due to be taken by other teaching unions.
It comes after the NASUWT, INTO and UTU confirmed its members will hold a half-day strike on February 21 amid the continuing row over pay and conditions.
Another teaching union in Northern Ireland, the NEU, is balloting its members on whether to strike.
The action will take place from midnight until midday.
It is expected that many schools will close until noon, as most teachers in the north are represented by the three unions.
While the majority of members of the NAHT backed strike action in a ballot, the union said it wanted to give more time for a pay dispute to be settled.
In the letter to members, reported by BBC NI, it told members while it stood "firmly and resolutely behind the strike action being taken by our sister unions" it "has decided not to call upon members to strike at this time".
The union has written to the employing bodies, the secretary of state and the leaders of the five main political parties urging for negotiations to help resolve the pay dispute by the end of the month.
"We have implored you to find a settlement to resolve this dispute," the NAHT letter said.
"Time is running out ahead of planned strike action, and the responsibility and power to solve this rests with you.
"If you have not resolved this dispute by 12.00 noon on Tuesday 28 February 2023, the NAHT (NI) Executive will consider all steps, including a request to our national executive, to exercise the membership's mandate to take strike action.
"This is an unprecedented warning from the school leaders in Northern Ireland."
