Widespread travel disruption is expected on Friday with the latest strike by bus and train drivers.
Translink workers who are members of Unite, GMB and Siptu will stage a 24-hour stoppage beginning at 00.01am on December 22.
It follows a two-day strike last week, which prompted criticism from representatives of the retail and hospitality sectors.
The strike is aimed at securing a cost-of-living pay increase. Money to resolve public sector pay claims was earmarked in the financial package for a restored Stormont executive tabled by the British government.
However, in the absence of a deal, the unions believe Secretary of State Chris Heaton-Harris should release the funds.
Siptu regional organiser Niall McNally said: “Chris Heaton-Harris is consciously making public sector workers and funding for public services a hostage to fortune.
“Indeed, the weaponising of public sector funding and public sector workers’ pay in this way amounts to a divide and conquer strategy to advance the secretary of state’s political agenda.”
Irish Congress of Trade Unions (ICTU) assistant general secretary Gerry Murphy has written to the secretary of state asking for a face-to-face meeting.
“We have expressed our appreciation that you have accepted that public sector pay needs to be settled and that you have the resources to settle it,” the letter said.
“This funding must be made available to settle these related industrial disputes now.”
The Northern Ireland Office said there was no further response beyond what Mr Heaton-Harris said on Tuesday.
“We stand ready to introduce a package of measures that have been worked on together should the DUP reach a decision to proceed,” he said as the talks concluded at Hillsborough Castle.