The British Chancellor of the Exchequer Gordon Brown has announced a financial package worth £35 billion Sterling (€51.5bn) over the next four years aimed at bolstering the return of devolved government in Northern Ireland.
The Irish Government is to provide £400m Sterling (€589m) towards a fund for the improvement of cross-border roads.
The multi-billion pound package is seen as being critical to hopes that power sharing will return at Stormont by next Monday's deadline.
After meeting the leaders of the North's political parties today, Mr Brown said that in addition to the £35 billion pledged to a new Executive over the next four years, devolved ministers would be able to access £1 billion to enable them to do a number of things to improve infrastructure and job prospects.
Mr Brown also revealed that the British government had signed a retail consortium agreement with major companies to provide possibly 5,000 jobs over the next few years.
He also confirmed that Sir David Varney, the former head of the Inland Revenue, had been asked to carry out a review of the different tax rates between the North and the Republic.
Minster for Finance Brian Cowen said the dual-carriageway road stretching to Derry and Donegal would remove the single biggest impediment to the future development of the North West and the border counties.
"It will be the biggest and most important cross-border project ever on this island," he added. As Monday's deadline for devolution nears, Mr Cowen said Gordon Brown's package offers a real opportunity for economic progress to accompany political stability in Northern Ireland.
"This unprecedented investment has been made possible through the joint contribution of the Irish and British Governments and will benefit everybody on this island.
"The agreement on a major cross-border roads programme and a new North/South research and innovation fund represent the type of imaginative and ambitious policies that we need to pursue to secure peace and build future prosperity."
The chancellor also supports wide proposals benefiting Northern Ireland contained in the Government's National Development Plan 2007-2013. Mr Cowen said he now looked forward to the progression of projects like the Ulster Canal, Narrow Water Bridge as well as tourism and regional development.
"Work is already under way on a number of other projects, such as the re-opening of border roads, City of Derry Airport, the North West Gateway Initiative, electricity interconnection and the single electricity market," he added.
"There is also huge untapped potential for improving public services such as health and education through working together." In a television interview this morning, Mr Brown confirmed that the package would be worth around £50 billion over 10 years.
Asked about today's meetings, he said: "I want to assure them that the new Executive, reconstituted, will be put on a firm and secure financial footing so that they will be able to make the investment in infrastructure that they need in Northern Ireland to be able to finance education and the other services that the UK Executive is responsible for.
"I want to offer them a four-year package of funding. We're not doing that for other Government departments, but we will do it for the Northern Ireland Executive to get them off to the best possible start," Mr Brown said.
"I will then offer them capital expenditures for infrastructure development over a longer period of time, and the total package that we are talking about for Northern Ireland is something in the order of £50 billion over the next period of time.
"That is something that we can do to help Northern Ireland begin to improve its economy as well as improve its infrastructure."