Construction of a new dual carriageway between Londonderry and Aughnacloy could begin late next year, the Infrastructure Department said.
The building work was due to commence several years ago.
The most recent obstacle, a court ruling effectively meaning civil servants could not take major decisions in the absence of ministers, was addressed by legislation aimed at unblocking the logjam created by the collapse of Stormont power-sharing.
The Infrastructure Department said: “The A5 remains a very high priority for the department and it will now move immediately to carry out the necessary work to enable a fresh decision on the project to be taken during 2019.”
It confirmed construction work could begin in late 2019, subject to legal considerations and any further issues arising.
Parliament has passed the Northern Ireland (Executive Formation and Exercise of Functions) Act 2018, giving civil servants powers to take major decisions in the absence of ministers.
Construction Employers Federation managing director John Armstrong said the department moved speedily.
“As this decision is, ultimately, tied to the passing of the Northern Ireland (Executive Formation and Exercise of Functions) Act and its associated guidance, it is now critical that all Government departments follow the lead of the Department for Infrastructure by seeking to utilise the powers of the new legislation to bring forward a range of capital works, both public and private sector, which are currently unable to progress for a variety of reasons.
“It is also critical that we see consistency in application of the Act and its associated guidance by all Government departments as it must, in the continued absence of ministers, be the means by which greater certainty can be applied to all levels of public sector construction works.”
“Recent fatalities on the A5 have once again reflected the need for enhanced infrastructure to improve road safety on one of the most dangerous roads in Ireland.
“Sinn Fein are committed to the achieving social development and the economic regeneration of the north-west and the A5 is key to delivering this.”