Ministers from Northern Ireland and the Republic have agreed to spend £400m on cross-border road projects.
The news of the joint investment came after a meeting of the North-South Ministerial Council in Armagh.
Deputy First Minister Martin McGuinness said the road from Omagh to Donegal and the route from Belfast to Larne would become dual carriageways.
"Obviously where it is in our economic interest we have to work together," Mr McGuinness said.
First Minister Ian Paisley said that it was hoped that significant investment could be found to re-open the Ulster Canal between Clones in the Republic of Ireland and Upper Lough Erne.
"The restoration of this route of the canal will be a tremendous boost to tourism on both sides of the border," he said.
The Irish government has pledged £30m to the project, with the Northern Ireland administration agreeing to maintaining the waterway.
The meeting included members of the executive and Taioseach Bertie Ahern and other Irish ministers.
Mr Ahern said that the meeting had been "very good".
Martin McGuinness, Ian Paisley and Bertie Ahern arrive at the meeting
"We had an open and very honest discussion on a range of issues that are very important to people on all parts of the island and agreed real outcomes that will benefit both sides of the border," he said.
The council first met in 1999, but was spurned by the DUP. Before it started Mr Paisley said they were entering "new territory".
"We are meeting under a new aegis because of the alterations made during the negotiations to get this new government off the ground," he said.
DUP ministers had boycotted the council - set up under the Good Friday Agreement to increase cross-border cooperation - branding it "unaccountable" and "an embryonic united Ireland".