The DUP will host a delegation of business leaders, politicians and council officials at Westminster this week as they lobby for a £1bn City Deal for Belfast - despite threatening to vote against the Budget on which the money depends.
The delegation will head to London on Wednesday to tell the UK Government of its ambitious plans to help reignite Northern Ireland's economy through the proposed Belfast Region City Deal.
DUP Brexit spokesman Sammy Wilson MP and Mid and East Antrim Borough Council will host an engagement event at Westminster on Wednesday morning.
But Mr Wilson has been among the fiercest critics of the Government's handling of the Brexit negotiations and has repeatedly suggested that DUP MPs would be prepared to vote against the Prime Minister's Budget if she crosses his party's "red lines" on Brexit.
Last week the Ulster Unionists expressed fears that the DUP's threat to block the Budget could jeopardise City Deals for both Belfast and Derry, as funding would require approval by Chancellor Philip Hammond and the Treasury.
UUP councillor Stephen Nicholl said last night: "Given the complexities around the City Deal, any idea that you would go to war with the Treasury at this point over the Budget puts all of this at risk.
"It depends on building relationships with the Treasury to convince them it's a good thing."
The Belfast Region City Deal hopes to create around 20,000 new and better-paid jobs, as well as improving infrastructure, digital connectivity, visitor attractions and innovation hubs; and delivering a major skills and employability programme.
Local authorities have been working in close collaboration with the NI Civil Service, the Ministry for Housing, Communities and Local Government and the Treasury as well as higher and further education sectors to agree the priority projects for submission to Westminster.
Lindsey Millar, the Ulster Unionist mayor of Mid and East Antrim, will be among those attending the Westminster lobby event.
"The number one strategic priority of our council is growing the economy," Ms Millar said.
"We're delighted that we are continuing our negotiations to secure this significant investment into the borough and Northern Ireland as a whole."
The partner councils include Antrim and Newtownabbey, Ards and North Down, Belfast, Lisburn and Castlereagh, Newry, Mourne and Down.
Responding to the UUP's criticism last week, South Belfast MLA Christopher Stalford said the DUP "will always use our influence to secure the best outcome for Northern Ireland and for the United Kingdom as a whole".
He added: "It is not the desire of the DUP to vote against the Government's domestic agenda, but we would not sit idly by if there was a suggestion the Union could be broken or fractured."