Mass disruption is expected in Northern Ireland on Thursday, with tens of thousands of public sector workers due to strike over pay.

It comes with no end to a protracted political crisis that has left the British province without a devolved government for almost two years.

Around 15 trade unions representing teachers, civil servants, nurses and transport workers are expected to turn out at rallies, according to organizers.

The Irish Congress of Trade Unions estimates that 170,000 out of 220,000 public sector union workers will stop work to demand the release of held-up funding for pay increases.

The mass strike, a "coordinated day of action" billed by unions as the biggest since Northern Ireland was founded in 1921, will likely cause havoc to already crumbling public services.

Schools will close, and transport services will halt as several hundred service workers who salt roads during winter are expected to join the strike, which coincides with a cold weather snap.

Authorities said health care services would be severely depleted, although essential and emergency care would remain available.

The strike, estimated to cost the economy more than 10 million pounds ($12.6 million), comes as a political stalemate in the region approaches a two-year-long milestone.

In February 2022, the largest pro-U.K. party, the Democratic Unionist Party (DUP), withdrew from the Northern Ireland Assembly at Stormont because of post-Brexit trading rules it said undermined Northern Ireland's place in the wider U.K.

The DUP lost its place as Northern Ireland's biggest party in 2022 elections, giving the first minister post in the power-sharing executive to nationalists Sinn Fein, who want a united Ireland.

U.K. Northern Ireland Secretary Chris Heaton-Harris said Monday that a 3.3 billion pound package offered to the parties last month would be available on condition that the assembly restarts.

But on Wednesday – as the legal deadline for a return approached on Thursday – lawmakers failed to elect a speaker for the seventh time, as no candidate could command the required support.

Heaton-Harris said it was "disappointing" that no speaker was elected and indicated he would pass legislation to extend the deadline rather than call fresh assembly elections.

Of the 3.3 billion pound package on the table, 584 million pounds is earmarked for public sector pay increases.

The main unions say the money for pay rises should be released as soon as possible regardless of the suspended assembly.

But the DUP accuses London of using industrial unrest as a lever to end the party's boycott.

DUP leader Jeffrey Donaldson says the U.K. government in London has the money and the power to implement the pay awards immediately.