The prime minister has said she is determined to end the deadlock with the devolved governments over Brexit.
Theresa May will hold meetings with Scottish First Minister Nicola Sturgeon and her Welsh counterpart Carwyn Jones at Downing Street later.
The three have been at loggerheads over what happens to powers in devolved areas when they return from Brussels after Brexit.
Ms Sturgeon said she did not expect a deal to be reached at the meeting.
The UK government recently proposed the “vast majority” of powers returned from the EU would go straight to Edinburgh, Cardiff and Belfast rather than Westminster.
But it would retain control in 24 areas, at least in the short term.
It says this would be necessary to avoid different parts of the UK having different rules and regulations for things like food hygiene and health and safety when it leaves the EU.
But the Scottish and Welsh governments say it would effectively give Westminster a veto over some devolved responsibilities.
A series of meetings between the UK government and devolved administrations has so far failed to find a solution, although all parties agree that progress has been made in recent weeks.
Mrs May will hold talks with Ms Sturgeon and Mr Jones as part of a Joint Ministerial Committee meeting at Downing Street in bid to secure a breakthrough.
She said she would be making clear her commitment to a deal that “brings our country together, protects the security and prosperity of all our communities and business sectors, and reinforces our Union of nations”.
Mrs May added: “I am determined to secure a settlement that delivers an unprecedented democratic dividend for the people of Scotland, Wales and Northern Ireland, while protecting and preserving the precious Union that is at the heart of our past, present and future success.”
Ms Sturgeon said she was not expecting an agreement to be reached during the meeting as “there are no new proposals from the UK government on the table”.
She added: “At today’s meeting we and our Welsh colleagues will take the opportunity to set out what changes are required to secure our consent.
“While we remain determined to continue discussions on this issue, it is time for the UK government to show respect for devolution and accept that no changes can be made to Scotland’s devolved powers without the consent of the Scottish Parliament.
“Today is an opportunity for the UK government to demonstrate that it is genuinely committed to acting in the interests of the people of Scotland and to respect the democratically endorsed devolved settlement.”
Scottish Secretary David Mundell had been among those due to be at the JMC meeting, but he will not now attend after returning to Scotland on Tuesday due to the death of his mother Dorah at the age of 92.
What is the row about?
Whitehall analysis has identified 153 areas where policy in devolved areas is currently decided in Brussels.
The UK government’s Brexit bill had initially proposed returning all of these to Westminster immediately after Brexit.
But it has recently put forward changes that would see the “vast majority” of those EU powers instead returning directly from Brussels to Edinburgh, Cardiff and Belfast.
This would include in areas such as carbon capture, water quality and energy efficiency.
But it has named 24 devolved policy areas where it wants to retain power temporarily in the wake of Britain’s exit from the bloc, including in areas such as agriculture, fisheries, food labelling and public procurement.
The UK government says this is necessary to avoid different parts of the UK having different food hygiene or safety regulations.
But the Scottish and Welsh governments have repeatedly accused the UK government of a “power grab”, and have introduced their own Brexit legislation in their respective parliaments.
Nicola Sturgeon to meet Theresa May over Brexit row}