Transport Minister Martin Cullen is due to turn the sod on a new cross-border dual carriageway between Dundalk and Newry today.
The €122m project is being built by the Republic's National Roads Authority and the Northern Ireland Road Service.
The 14km dual carriageway will run from just north of Dundalk to the Cloghoge roundabout outside Newry and will link the A1 in the North to the M1 in the Republic.
When completed in 2007, the road will allow motorists to enjoy continuous dual carriageway from Belfast to Arklow in Co Wicklow.