The new Northern Ireland Assembly will meet later amid uncertainty over whether the DUP will support the election of a Speaker.
Ninety MLAs will gather in the chamber after last week’s Northern Ireland Assembly election saw Sinn Fein emerge as the largest party for the first time.
The DUP has already indicated that it will not nominate for the position of deputy First Minister, which will prevent the forming of a new Executive, as part of its protest against the Northern Ireland Protocol.
Unionists oppose the post-Brexit treaty because of the economic barriers it creates between Northern Ireland and the rest of the UK.
Party leader Sir Jeffrey Donaldson said his party will decide on Friday morning whether it will support the election of a Speaker.
Without a Speaker, the Assembly will be prevented from carrying out business.
Sir Jeffrey said his team of MLAs will be at Stormont on Friday to sign the roll.
Speaking on Thursday, he said: “We are committed to making the political institutions work but we’re also clear that we need to see decisive action by the Government (on the protocol),” he said.
Asked whether his party will nominate a Speaker, he said: “Our Assembly group will meet and come to final decisions on all of this.
“The Assembly meets tomorrow morning and parliamentary protocol determines that the first people to know are the people who actually sit in an Assembly, therefore we will make our position clear on this.
“We recognise that these issues need to be dealt with. As a party, we have been decisive, we have made our position clear and will continue to do so.”
Instead, former party MP Emma Little-Pengelly has been co-opted to replace her leader on the Stormont benches.
As the largest party, the new 27 Sinn Fein MLAs will take their position on the benches on the right-hand side of the Speaker’s chair for the first time.
It is entitled to nominate its Stormont leader Michelle O’Neill as First Minister, but she will not be able to take up the role without the DUP nominating a deputy First Minister.
Under the rules of the devolved power-sharing administration, both roles are equal and one cannot be in office without the other.
Since last week’s election, Ms O’Neill has repeatedly called for the DUP to re-enter the Executive so it can begin to tackle challenges such as the cost-of-living crisis and spiralling hospital waiting lists.
“There is no reason for that not to happen and it is not acceptable or not good enough that the DUP won’t turn up or won’t nominate for the position of Speaker or the title of First or deputy First Ministers.”
The Stormont sitting comes amid increased tensions between the Westminster Government and the EU over the working of the protocol – which forms part of the UK’s Withdrawal Agreement with the EU.
Foreign Secretary Liz Truss said the UK will have “no choice but to act” if the EU does not show enough “flexibility” over post-Brexit checks on goods going from Britain to Northern Ireland.