The Northern Ireland Secretary will meet the leaders of the main parties at Stormont later to press for the return of devolved government.
The Stormont Executive has been unable to fully function since February when first minister Paul Givan resigned as part of the DUP’s efforts to force action against the Northern Ireland Protocol.
Fresh Assembly elections returned an historic result at the weekend with Sinn Fein overtaking the DUP to become the first nationalist or republican party to emerge top at Stormont.
However the DUP, as the second largest party, must nominate a deputy first minister to serve alongside her in the joint office.
DUP leader Sir Jeffrey Donaldson has signalled the UK government must act over concerns about the post-Brexit trading arrangements before his party will nominate ministers to a new Executive.
On Sunday, Sir Jeffrey’s party colleague Jonathan Buckley said: “Either the secretary of state wants an executive, or a protocol – he can’t have both.”
He said his party received a mandate to ensure that concerns around the protocol are dealt with.
“We made clear some time ago that the time for listening, the time for talking, is now over, it’s time for action,” he told the BBC.
“We need stable government and fair government. At this minute in time no unionist-elected representatives support the Northern Ireland Protocol, that’s not a sustainable position.”
Asked will his party nominate a deputy First Minister to serve alongside a Sinn Fein First Minister in the joint office once the protocol has been dealt with, Mr Middleton said: “Ultimately we’re democrats, we accept the fact that the will of the people is there, that they want people to go into government.
“We’ve been sharing power in Northern Ireland for 15 years so it’ll be no surprise to people that we will be part of an Executive, if we can deal with the issues that appear are outstanding, and that has been clear from the outset.”
Pressed on the point, he replied: “Yes, because we’re democrats.”
Brandon Lewis will meet the leaders of the five parties which formed the last Stormont Executive in a series of meetings across Monday.
Speaking ahead of the meetings, Ms Lewis acknowledged his government “have to address” issues relating to the protocol.
But he urged the parties to form an Executive as soon as possible.
Tory MP Andrew Griffith, the director of policy at No 10, was asked by The Westminster Hour on BBC Radio 4 if the UK Government was prepared to act unilaterally over the protocol.
Mr Lewis is due to have a call with Irish Foreign Affairs Minister Simon Coveney following his meetings with the parties.
“The people of Northern Ireland deserve a stable and accountable devolved government and I will continue to urge the leaders of Northern Ireland political parties to fulfil their responsibilities and form an Executive as soon as possible,” he said.
“This process must begin with the nomination of an Assembly Speaker to allow legislation to progress and address the important issues affecting the people of Northern Ireland.
“However, the people of Northern Ireland need a stable and accountable government that delivers on the issues that are important to them. That is why we urge the parties to come together and form an Executive.
“I will remain in close contact with the party leaders but it is for the parties to agree on a way forward. New Decade New Approach specifically introduced measures to support a process led by the parties. This is in the best interests of the people of Northern Ireland and I urge the Northern Ireland parties to work together towards a brighter future.”
The party leaders are due to meet at Parliament Buildings later in the afternoon.