The French Polynesian party, Te Hono, says it will fight in court any French attempt to stop Tahitian from becoming an official language.
A court in Papeete is expected to rule on a French appeal against last year's decision of the French Polynesian parliament which gave the territory's five Maohi languages official status in court.
But the French state says the laws are against the constitution.
The secretary-general of Te Hono, Tina Cross, says many Polynesians don't speak the language of the court, which is French.
She says if the French appeal succeeds her party will take the case further.
"We are ready to go to the European Court on Human Rights and even we go to the United Nations to fight for our reo, reo Maohi."