Supply chain delays due to Covid-19 have pushed out the urgent repair of a retaining wall in Porters Pass.
Waka Kotahi journey manager Tresca Forrester said the steel needed for the repair had only just been delivered.
Work on the retaining wall, west of Springfield on State Highway 73, will take place over the next 10 weeks.
The road will be down to a single lane for 1.2 kilometres past the site with a 30km/h speed restriction for the duration of the work.
On weekends, traffic management with a Stop/Go sign may be used at peak times, to ensure people can get to nearby skifields without delays.
"We have talked to the skifield operators on SH73 and are in close communication with them if they open in June or early July. In the event of snow falling on the highway, crews will disestablish for the day and if possible, open the route to two lanes."
The work site is on a stretch of highway that climbs over a hill with no visibility from one end to the other, so Forrester said it was important motorists obey the traffic signals.