They issued a statement after the pro-independence FLNKS movement restated its position that Matthew and Hunter islands belonged to Vanuatu's heritage.
The three said last November's independence referendum showed a majority of New Caledonians wanted to stay French.
They said they would therefore oppose any attempt to dispossess the country of part of its land and wealth.
FLNKS leader Daniel Goa said unlike the people of Vanuatu, the Kanaks had no cultural links to the two islands.