The Executive remains committed to the £330 million upgrade of the A5, Martin McGuinness has told a Stormont meeting on the troubled project.
The deputy First Minister said the upgrade of the road between Londonderry and Aughnacloy in Co Tyrone was facing a potential 18-month delay after a successful legal challenge against the plan, but said funding would be made available once the green light was obtained.
Mr McGuinness was addressing a private meeting at Parliament Buildings with politicians from north and south who represent areas impacted by the proposed cross-border corridor.
The A5 plan formed part of a scheme to develop a new transport route between Dublin and the north west of Ireland.
The project has been dogged by problems from the outset, with the Irish Government having reduced its initial financial commitment due to the economic situation south of the border.
Last month, the Northern Ireland section hit its own problems when a High Court judge quashed a decision by Roads Minister Danny Kennedy to proceed with two stretches - from New Buildings to north of Strabane in Co Londonderry, and from south of Omagh to Ballygawley in Co Tyrone.
Mr Justice Stephens found in favour of the Alternative A5 Alliance lobby group, which had challenged Mr Kennedy by means of a judicial review.
Justice Stephens found that an appropriate habitats directive assessment on the potential impact on the River Foyle and River Finn Special Areas of Conservation (SAC) had not been carried out.
The court decision threw the project into uncertainty as of the £330 million allocated by the Executive to the development, £100 million was set to be spent in this financial year.
Mr Kennedy is trying to convince Executive colleagues to let him retain that money within his department to divert to other projects that are almost ready to go.
One alternative build is the planned upgrade of the A6 between Belfast and Londonderry.
Sinn Fein MP for West Tyrone Pat Doherty, who chaired the meeting, said it was heartening to hear the project remained an Executive priority.
"The deputy First Minister, Martin McGuinness, stated that while there could be a year to 18 months delay, once it has been given the go-ahead following the resolution of any outstanding issues, that the road would receive immediate funding to push forward with what is essentially a project of huge economic significance," he said.
SDLP West Tyrone MLA Joe Byrne said: "I welcome the reaffirmed commitment by the office of First and Deputy First Minister and the Executive, that building the A5 remains a priority.
"The delay in this building project caused by the legal challenge is frustrating but it is only a temporary setback. Every party north and south wants this road to go ahead. It will go ahead."
Alternative A5 Alliance spokeswoman Laura Kwasniewska said the dual carriageway plans did not represent value for money.
"What has been ignored in this is the fact this is a road scheme that is not justified by the traffic figures," she said.
Ms Kwasniewska said it would be more appropriate to make changes to the current road, such as introducing more passing lanes, better lighting and safety measures.
"That would represent much better value for money," she added.
Regional Development Minister Danny Kennedy said: "My department has received funding for the A5 dual carriageway project as the result of an Executive decision. As Roads Minister, I am keen to see the upgrading and improvement of the entire strategic network.
"The A5 project has been delayed and my department will continue to work through the relevant issues.
"We estimate that the delay will be somewhere in the region of a year to 18 months, which is why it is incumbent on me that other schemes which may be in a position to be progressed ahead of it are given full consideration by the Executive.
"I intend to bring to the Executive proposals detailing other options, such as moving forward with procurement on other possible schemes. That approach provides the best possible support for the construction industry.
"In the meantime, my department continues to develop a number of schemes to a procurement-ready position, should additional funding become available."