The French Polynesian government has called on the mayor and council of Rikitea on Mangareva to show common sense and allow a shipment of gravel to be offloaded.
The island leaders say they will block the shipment to keep the peace on the island after an anti-nuclear group Association 193 said the material being shipped for road construction was irradiated.
The ship is due to arrive in Rikitea this weekend from Hao atoll where France had a military base during the period it carried out its nuclear weapons tests.
The public works minister Albert Solia has sought to allay fears, saying the material is from buildings and hangars that used to house 3,000 soldiers until 1970 when France stopped its atmospheric nuclear tests.
Mr Solia says since 2009 the walls and pillars of those buildings have been broken down and in 2011, three analyses showed there was no contamination.
From 1966 to 1996, France carried out 193 nuclear weapons tests in the South Pacific.