UK ministers are to make what they call 'a considerable offer' to try to end the stalemate in Brexit talks with the Welsh and Scottish Governments.
However it's likely to be rejected at a meeting in London today although there are signs of a split between Welsh ministers and their counterparts from Scotland on what approach to take.
The deadlock is over the impact on devolution in Wales and Scotland of the UK Government's EU Withdrawal Bill which Carwyn Jones and Nicola Sturgeon have described as a 'naked power grab.'
They say that when powers over rules and regulations in areas that are devolved such as farming and fishing return to the UK they should be passed straight to Cardiff and Edinburgh.
Until now the UK Government has insisted that those powers should first be operated on a UK-wide basis.
After months of talks it's now agreed that 'the vast majority of powers will automatically flow from the EU to the devolved administrations.'
Under the new plan ministers in London would retain a veto on the use of those powers 'in a small number of areas' in order to ensure businesses don't find themselves dealing with different rules and regulations in different parts of the UK.
The offer is being announced by David Liddington, who acts as Theresa May's deputy, at a meeting of the Joint Ministerial Council, which brings together ministers from the devolved nations and the British Government.
However the offer is likely to be rejected because neither the Welsh and Scottish governments think it goes far enough.
Although the two have been working very closely over the last year to try to force the UK Government to back down, in the run up to today's meeting they've adopted different tactics with Scottish ministers making it clear they'll reject the offer.
That was described earlier this week as 'unhelpful' by the Welsh Government who believe there are further concessions to be made and want talks to continue.
It was in turn criticised by Plaid Cymru who accused Carwyn Jones of being 'complicit' in what they call Westminster's power grab.
The Welsh Government may be taking a more conciliatory approach in public but it's position isn't a million miles away from that adopted by the Scottish.
Privately those close to the negotiations say the offer isn't enough which means AMs will be advised to refuse consent to the Withdrawal Bill as it affects Wales.
The UK Government isn't obliged to recognise such a vote but it would cause a major constitutional row between the different nations.
What's more, the lack of agreement is likely to cause problems sooner rather than later because it means the Welsh Government will push ahead with its Continuity Bill, which would claim those disputed powers without agreement from London, as early as next week.
From the outside it may not seem very exciting, but it has the capacity to cause a constitutional crisis.