The existing road that winds through Te Uruwera Forest is hard on vehicles.
There are fears Government funding to upgrade the road to scenic Lake Waikaremoana will expire before any work can be done.
Recently Ngāi Tūhoe, which manages the lake in the Te Urewera region west of Gisborne, came under fire from Regional Economic Development Minister Shane Jones after it voiced opposition to upgrade State Highway 38, which runs alongside the lake, with petro-chemical bitumen.
That forced Jones to cancel a Provincial Growth Fund (PGF) announcement to tarseal the mostly-gravel highway.
Tūhoe is instead trialling a non-chemical alternative. It says visitors dumping vast amounts of rubbish in their wake is only part of the reason they are experimenting with the "natural" paving method.
But Wairoa Mayor Craig Little expressed fears that if the trial didn't come to an end soon, the road may miss out entirely on funding.
"Tarseal as a road surface is proven and, while I am impressed with the natural road sealing alternatives presented by Tūhoe, they are unproven and there is a lot more testing to go," he said.
"The funds for sealing this section of SH38 are available now and it would be a shame to lose that opportunity."
Little said the council's role was to support and provide the best services to ratepayers and residents.
"That is why we are advocating to have this section of national highway sealed."
But Tūhoe leader Tāmati Kruger has described the council's position as a "rape and pillage mentality ... of unchecked tourism".
Jones previously said the Government hadn't yet disbanded the proposal to contribute towards upgrades of SH38, but Tūhoe's "environmentally friendly" trial was "hillbilly thinking".
A spokeswoman for the Minister on Thursday said the future of SH38 and the funding rested in the hands of both Tūhoe and the Wairoa District Council.
"Our officials from the Provincial Development Unit will do what they can to facilitate helpful discussions," she said.
"However I'm sure you'll appreciate the PGF is a time-constrained fund and that there is a vast amount of other projects seeking funding."
New Zealand Transport Agency spokesman Ross I'Anson said it was working with Tūhoe and the Wairoa and Whakatāne councils on a strategic case for the entire corridor between the two locations.
Calls for Lake Waikaremoana to be closed to visitors if rubbish dumping does not improve.
It recently met with the parties to plan the next phase of the business case, which would help improve access while also aligning with the principles of Te Kawa o Te Urewera, I'Anson said.
"The Green Road, or Nature Road, is an environmentally-friendly alternative to bitumen sealing, however further trials will need to be done to ensure that the road surface is safe and resilient enough to carry state highway traffic long term."
The agency and councils would continue to work "closely" with Tūhoe on the trial.
Tūhoe took over the lake's management from the Department of Conservation, as part of an historic Treaty of Waitangi settlement.