There'll be a warning to leaders of the Welsh and Scottish governments to 'pull together' during Brexit negotiations or risk making the UK 'a poorer country that is divided at home and a weaker player on the global stage.'
The warning will come from David Lidington, who acts as Theresa May's deputy, when he speaks at the Airbus factory in Broughton later.
It'll be the latest in a series of 'Road to Brexit' speeches by cabinet big-hitters designed to set out what the government sees as the opportunities of leaving the European Union.
Mr Lidington will also use his speech to make a fresh attempt to defuse a standoff with the Welsh and Scottish Governments over claims that the UK Government's EU Withdrawal Bill is a 'power grab.'
That's only one of a number of disagreements between the agreements over the negotiating stances taken by Westminster figures.
In his speech at Broughton, David Lidington is expected to say that the administrations should push those differences only so far:
There's little sign of any pulling together when it comes to the EU Withdrawal Bill.
Carwyn Jones and Nicola Sturgeon have condemned it as a 'power grab' because it insists that some rules and regulations which will return from Brussels should continue to be controlled by Whitehall.
The UK Government hoped to end the stalemate last week by making a concession which would see those powers transferred directly to Cardiff and Edinburgh, albeit with a continuing veto for ministers in London.
Despite the concession, talks failed and there were demands for a further meeting this week.
In his speech, David Lidington will explain why he believes the change and the alterations to the bill which would follow, represent such a 'considerable offer.'
He'll also defend the need for a veto to continue in some areas.
'The UK Government must come to its senses'
Plaid Cymru has called for Mr Lidington to use the opportunity of the speech to commit to continued membership of the single market and customs union.
The party's Brexit spokesperson Hywel Williams said he also wants to see other major changes to the UK Government's approach.
Whether or not Britain negotiates ways of staying in the single market and/or the customs union either permanently or during a transition period is a matter of intense debate amongst and within political parties.
Labour leader Jeremy Corbyn is expected to announce today that his party has agreed a position which is that the UK should look to form a new customs union with the rest of the EU, even if that means restrictions on other trade agreements.
While there's been confusion about the UK party's position until now, Welsh Labour leader Carwyn Jones has been clearer about his support for remaining in a customs union.
Plaid Cymru will try to highlight that difference with a debate in the Assembly chamber later this week.
As an opposition debate it won't commit the Welsh Government but Plaid says a strong vote will give Wales 'more leverage' in Brexit negotiations.
Criticising Labour's confused position, Leanne Wood urged Welsh Labour to make clear it supports remaining in the current customs union.