The UK government was expected to call the second general election of this year in Northern Ireland on Friday after UK and regional lawmakers failed to resolve a standoff over post-Brexit trade rules.

A deadline to resume devolved government in the Stormont Assembly passed at midnight, prompting Northern Ireland Minister Chris Heaton-Harris to tweet that he was “extremely disappointed”.

“Today, Stormont could make decisions to ease people’s challenges. Instead, as Secretary of State, I have a legal duty to act… I will provide an update on that,” he tweeted.

UK Environment Secretary Therese Coffey, meanwhile, said the failure to end the stalemate meant there would now “definitely be an election”.

Jeffrey Donaldson, leader of the pro-British Democratic Unionist Party, defended his party’s blocking of restoring power-sharing as part of its protest against the so-called Northern Ireland Protocol, which governs post-Brexit trade rules.

He said his party “cannot nominate ministers to an executive bound to enforce a protocol that harms our economy, harms our people and prevents us from accessing medicines and other essential supplies from the rest of the UK “.

Donaldson added he was “ready to form an executive as soon as that solution is found,” but his party had waited nearly three years.

“We need a solution,” he stressed.

The legal deadline for the creation of a joint executive of pro-Irish nationalists and pro-British unionists came after the provincial parties made a last-ditch attempt to restart the devolved assembly.

In a contentious session on Thursday, lawmakers convened briefly in special session for the first time in months, but failed to choose a speaker, preventing the formation of a new government.

The DUP has been boycotting the gathering since February, demanding that the minutes be revised or scrapped altogether.

Britain’s new prime minister, Rishi Sunak, had begged the parties to “return to Stormont” and argued that the people of Northern Ireland “deserve a fully functioning and locally elected executive branch,” his official spokesman said on Thursday.

Heaton-Harris, an arch-Eurosceptic who was only appointed to his role on September 6, has insisted that if the UK government’s deadline is Friday, he would not hesitate to call general elections, with December 15 is the probable date for the new election.

Northern Ireland has now been without a functioning government for nine months and the pro-Irish party Sinn Féin won a historic first election in May, further complicating the political situation.

Sinn Fein leader Michelle O’Neill — who would become first minister if the executive branch were restarted — condemned the DUP’s “permanent standoff with the public, a majority of which it does not speak for or actually represent.”

The DUP insists the protocol – agreed by London and Brussels as part of Britain’s 2019 Brexit deal – must be addressed first.

It claims the pact, which effectively keeps Northern Ireland in the European Union’s internal market and customs union, weakens the province’s place within the UK.

Many unionists also argue that this threatens the delicate balance of peace between the pro-Irish nationalist community and advocates of continued union with Britain.

The protocol was agreed to avoid the return of a hard land border with the Republic of Ireland, which remains an EU member.

Abolishing this hard border was a key element of the 1998 Good Friday Agreement, which ended three decades of sectarian violence in Northern Ireland.

The Conservative British government, which has had three prime ministers in two months, has urged Brussels to agree to major overhauls to the protocol. London is also in the process of passing controversial legislation to unilaterally overturn it.

That has raised fears of a trade war and deteriorating ties with Europe when the economic landscape is already bleak.