But Dr Cullen's spokesman said no settlement had yet been reached with the North Island iwi collective.
"It is too early to speculate on its impact on the relativity clause negotiated as part of the Ngai Tahu Deed of Settlement," he said.
He said the Crown reported every October to Ngai Tahu on the total amount spent on Treaty settlements in "1994 dollars".
At the heart of proposed settlement are nine central North Island forests - Kaingaroa, Horohoro, Whakarewarewa, Crater, Waimihia, Marotiri, Pureora, Waituhi and Taurewa.
Under the proposed deal, Tuwharetoa will also be offered the opportunity to buy the Lake Taupo and Lake Rotoaira forests from the Crown.
The forests are administered by the Crown Forestry Rental Trust, which holds about $240 million in rental revenue collected from foresters renting land in the nine forests.
Carbon credits are also understood to be on the negotiating table as part of the deal.
Tainui, the first iwi to complete a Treaty settlement with the Crown, also has a relativity clause like Ngai Tahu's.
- NZPA