Maori Council executives say they are relying on tribes to fund judicial review of the process by which the Government decided to partially privatise the hydro electric power generator Mighty River power.
Meetings and teleconferences on Tuesday between the council, iwi, hapu, land trusts, and representatives of the Maori King, agreed to go to court.
The council is continuing its discussions with an aim to have 100% backing by the end of the week.
It will argue the Crown is going ahead with a share float when Maori proprietary rights to water have not been recognised.
Council solicitor Donna Hall says tribes will need to pay for most of the court action.
She says they're speaking to iwi and hapu and expect to get financial commitment from the tribes, who will have to meet the bulk of the costs.
Mrs Hall says the Maori Council will be able to contribute some money.
The Government maintains that in common law no one owns the water.
It says that Maori do have rights and interests in water - which will be addressed through treaty settlements, the Government's Fresh Start for Fresh Water programme and talks with iwi leaders.
Prime Minister John Key says the partial sale of Mighty River Power does not affect the Crown's ability to recognise Maori rights and interests in water.
One of the Maori Council's water-rights claimants, Waikato hapu Pouakani says the pathway to negotiation has almost closed, and it's willing to contribute to the cost of going to court.
Chairman Tamati Cairns says the hapu won't be entitled to legal aid.
He says there is no financial assistance to launch a case against the Crown, yet the Crown is totally funded by the taxpayer.