Public servants could see their working week reduced from July this year following an independent review.
In 2013, the Haddington Road Agreement increased public servants' working week to 37 or 39 hours.
However an Independent Body has recommended they return to pre-2013 levels.
The proposal would benefit more than 150,000 public sector workers including nurses and clerical staff, and cost an estimated €180m.
SIPTU Deputy General Secretary, John King, says the government's due to make a final decision on it this week.
"It was agreed with the Government as part of the negotiations on the existing public service agreement that they would set in place an independent body and to make a report to Government, and we understand that report has now gone to Government.
"Hopefully we will see the restoration of these hours to their pre-2013 levels effective from the first of July this year."
