Jeffrey Donaldson has left open the possibility that the DUP will block the election of a new Speaker when the Stormont Assembly meets on Friday.
The DUP leader said on Wednesday that his party had yet to make a decision on whether to vote to elect a new Speaker when MLAs meet in the chamber in two days’ time.
The election of the new speaker is the first item on the agenda for MLAs following the election and requires cross-community support from nationalist and unionist members.
The DUP is refusing to return to the power-sharing Executive until its issues with the Northern Ireland Protocol are resolved.
Mr Donaldson told BBC Radio Ulster that his party would decide by Friday whether to elect a new Speaker.
He said: “We will be there on Friday. Our members will be there to sign the roll. We will make a decision as to how we proceed. We’ll get the group together and we’ll determine how best to take this forward.
“I’m waiting to see what the government has to say. So, that is the priority right now, to ensure that what the government say is moving us in the right direction.
“I’m simply saying that we will need to make a decision on that. That’s one of the decisions we’ve got to make.”
US foreign secretary Liz Truss is set to tell the EU that the dispute over Northern Ireland cannot drag on, amid concerns in EU capitals the UK is poised to take unilateral action on the post-Brexit arrangements in the region.
Mr Donaldson said on Tuesday he would not leave the House of Commons to take up his seat in the Northern Ireland Assembly until issues around the protocol are resolved.
On Wednesday, he stressed there was “unfinished business” at Westminster. “If the Government are going to act, then I believe, as the unionist leader, I need to be here to see that through because it’s fundamentally important.
“There isn’t a single Unionist Member of the Assembly elected last week who supports the protocol. We can’t go on with that kind of situation.”
He also said he did not anticipate any DUP candidate who failed to secure a seat in the Assembly would be co-opted to represent Lagan Valley while he remains at Westminster.
He said the seat would not remain “vacant” and that an announcement on his temporary replacement would be made in the coming days.
Sinn Féin has criticised the DUP’s suggestion that it may choose not to elect a new speaker .
Speaking after a meeting with Minister for Foreign Simon Coveney, Sinn Féin's northern leader Michelle O'Neill said the speaker has to be elected.
She said: “What we need to see is the positions filled — first minister, deputy first minister, all the ministerial positions filled — and let’s get down to doing business.
“I don’t think it is good enough. It is not good enough for the people here that the DUP is holding society to ransom, punishing society, preventing the establishment of a Speaker and an Executive to actually respond to the things people are worried about.
“I don’t think it is acceptable the position Jeffrey Donaldson has articulated today.”
Ms O’Neill said her meeting with Mr Coveney had been “constructive” because Sinn Féin has a “shared interest” in restoring the Executive.
“It is obvious that we made the case that we want the Executive up and running, working on behalf of the people,” she said.
“There should be no more delays. That should have happened by now. We had the election results last week. The people have had their say.
“We encourage all parties to turn up on Friday.”
Ms O’Neill insisted that the Northern Ireland Protocol cannot be scrapped.
“The protocol is here to stay. There are ways to smooth its implementation, and we are certainly up for that, but the rhetoric from the British Government in the last number of days is serving only to pander to the DUP.”
Minister for Foreign Affairs Simon Coveney is in Belfast meeting political leaders following last week's elections.
Mr Coveney met Sinn Féin vice president Michelle O'Neill at 9am, and has already had what sources described as a "long phone conversation" with Democratic Unionist Party (DUP) leader Jeffrey Donaldson, who is in London.
Mr Coveney is also set to meet senior figures in the Alliance Party and Doug Beattie, leader of the Ulster Unionist Party (UUP).
Talks will focus on restoring the institutions of the Belfast Agreement and getting an Assembly and Executive up and running following the election.
Former DUP leader Edwin Poots on Wednesday said you can have the Northern Ireland Protocol or the peace process but not both. He said the DUP could form a government but was not ready to do that until this issue was significantly dealt with.
We want a peace process but not one divided by nonsensical rules imposed by the EU to protect he single market, he told RTÉ’s morning Ireland .
Elsewhere, UK communities secretary Michael Gove has said the UK will continue to negotiate with the EU to resolve differences over the Northern Ireland Protocol but said "no option is off the table".
Foreign secretary Liz Truss has made clear her frustration at the lack of progress in talks with Brussels amid reports the UK could unilaterally abandon the protocol.
Asked on BBC Breakfast if the government was going to “tear up” the agreement, Mr Gove said: “No. We are going to negotiate with the EU in order to get the best possible outcome for the people of Northern Ireland, but no option is off the table.
"Liz Truss will be meeting Maros Sefcovic, the European Commission vice president, tomorrow. They have a good relationship. They will try to make progress tomorrow. I know that both of them are fully committed to making sure we resolve some very difficult issues that have arisen.
"You would expect a UK government when it is thinking about the security of the entire United Kingdom to say that there is no option that is off the table and that is absolutely right."
Efforts to form a powersharing government in Stormont are deadlocked as Mr Donaldson said his party would not go back into the Executive until there was “decisive action” on the Northern Ireland protocol.
With no immediate prospect of a resolution, the North is facing a long period of political stalemate which could last up to six months and, potentially, a fresh election.
The other Northern parties and the Irish, British and US governments have urged the DUP to nominate a Deputy First Minister who would share office with Sinn Féin’s Michelle O’Neill as First Minister.–Additional reporting PA