The opening of the massive Transmission Gully motorway project is likely to be further delayed.
Transmission Gully construction Photo: RNZ / Rebekah Parsons-King
The 27km four-lane motorway north of Wellington will be a major new arterial route into the capital.
The $850 million project was initially slated for completion in April next year but was pushed back by a month because of the Kaikōura earthquake.
The Transport Agency said this year that construction problems and bad weather meant the May date was being reassessed.
A Porirua City Council official has told news website Stuff the opening is now likely to be November next year.
The council told RNZ it was not appropriate for it to comment any further.
NZTA would not confirm the date but said it anticipated the motorway would be finished later in 2020.
NZTA general manager for transport services Brett Gliddon said it was a highly complex project being constructed on very difficult terrain.
He said progress has been slower than anticipated but work was progressing as quickly as possible.
"However, this must be done safely and to a high standard. As with all projects there are a number of factors which can influence an opening date and there is still a considerable amount of work to do."