The Transport Agency says it will not open the highway through the Manawatu Gorge until its satisfied the road is safe.
Continuous slips and the threat of rockfalls have closed the road on State Highway 3 since 18 August this year and could keep it shut for up to another two months.
The agency's national operations manager says the slip is very difficult to stabilise and there is a high probability of further rockfalls.
David Bates is confident the road will reopen when the remaining loose material is brought down from the slip face.
Manawatu's economic development agency recently estimated the closure's cost to local businesses at $62,000 per day.
