One hundred and thirty members of the Defence Forces are unable to return home to their families tomorrow as scheduled after a tour of duty in the Golan Heights.
The troops are part of the UNDOF mission in the Golan Heights.
They were scheduled to fly from Syria to Beirut and then to Dublin, with a planned landing here at 9.40am tomorrow.
The delay to their travel schedule has occurred because the Lebanese authorities have not yet granted approval of the landing clearance in Beirut for their aircraft.
This is the second time in a year that the return of troops has been delayed.
The troops have finished a six-month tour of duty and the soldiers to replace them have already arrived.
A spokesperson for the Department of Defence said: "The United Nations is responsible for organising the rotation flights to transport the current UNDOF contingent back to Ireland.
"We have been advised by the UN that the Lebanese authorities have not yet granted approval of the landing clearance in Beirut for the aircraft scheduled to transport the 59th Infantry Group.
"Defence Forces personnel on the ground are liaising with the local United Nations personnel, who are doing their utmost to resolve this situation," said the spokesperson.
"At the request of Minister Paul Kehoe, Ireland's permanent mission in New York is engaging directly at the highest levels with the UN in New York, with a view to resolving the situation as quickly as possible.
"Defence Forces personnel remain at their base at Camp Faoar in Syria pending resolution of the situation.
"Families have been informed of this delay by designated family liaison officers, and further updates will continue to be provided as they become available," the spokesperson added.
However, Fianna Fáil defence spokesperson Jack Chambers said: "This is yet another example of the failure of Minister Kehoe and the Department of Defence to properly arrange the safe and timely return of troops who have proudly served Ireland abroad on a UNDOF mission.
"Blaming the United Nations and putting this latest failure on their doorstep is not an acceptable excuse.
"This mix-up and subsequent delay that has been caused to these troops return home after a lengthy stint abroad, was just as easily as avoidable as the last."
One wife, who did not wish to be named, said: "Myself and the children are devastated, we have gone through a long arduous six months without him."
PDFORRA confirmed they have just been made aware of an issue.
Ger Guinan said: "We are absolutely gutted for their families and we are deeply disappointed this has arisen, especially as it occurred last October too."