During a French naval mission to the small uninhabited islands in January, France reportedly took action to re-enforce its sovereignty, when officers landed, polished a plaque and painted the French flag on a rock.
Johnny Koanapo, who has represented Vanuatu's claim in talks with France, said the unilateral move complicated the negotiations.
"We, the people of Vanuatu, will not take this lightly. We are very concerned and we want France to give a proper explanation," he said.
