First Minister Mark Drakeford will tell business leaders later that a no-deal Brexit represents the worst case scenario and is wholly unacceptable.
He will be addressing the Deeside Business Forum’s Brexit Business conference at Theatr Clwyd.
Meanwhile Theresa May has reached out to union leaders as she makes an 11th-hour attempt to reach out to her political opponents to get her Brexit deal through the Commons.
Downing Street said the Prime Minister had "constructive" phone conversations about her Brexit deal with trade union big beast Len McCluskey of Unite, a Brexit supporter and close confidant of Labour leader Jeremy Corbyn, as well as Tim Roache of the GMB.
Number 10 also confirmed ministers would "consider very seriously" moves by Labour MPs to safeguard workers' rights after Brexit in an attempt to win support for her deal, if the backbench amendment was selected by the Speaker.
The amendment would keep EU rules on pay and conditions, health and safety issues, and environmental standards.