South Westland businesses looking at a Haast-Hollyford road say the road can be built for $220 million and they have overseas investors lined up to pay for it.
The 108km route, which has been mooted as far back as the 1870s only to be shelved many times, would link the West Coast with Milford Sound to complete one part of the South Island loop.
Former Westland mayor Durham Havill, chairman of the Westland District Council's property company which has been looking at the proposal, would not reveal who the backers were, except to say they may come from two separate countries.
A $205m conditional memorandum of understanding had been signed.
Private investment was the only way the road could be built in the current economy, he told NZ Newswire.
"We are confident and we believe it is very realistic."
It was estimated the road could take about three years to build. About 78km would be completely new road and 30km would need to be upgraded.
The road would be a toll road - they were considering charged $20 per person - for the first 30 years before being handed over to the council.
Mr Havill said the project had the support of Prime Minister John Key and other ministers.
It only went over a "small corner" of the South Westland National Park, a world heritage area.
He acknowledged there would be environmental opposition to the road, but said there were environmental benefits in knocking 355km off the current trip.
Westland Mayor Maureen Pugh said handing the project over to business people had proved far more effective than trying to get national or local funding for the road.
It was not a done deal yet but they would continue to chip away.
"If it's a really good business case it will stack up and investors will be easy to find," she told NZ Newswire.
"We are a lot closer than we have been in 50 years."