CHERBOURG, France (Reuters) - A shipment of 308 pounds of U.S. weapons-grade plutonium arrived in the French port of Cherbourg Wednesday, despite protests by anti-nuclear campaigners who fear it is vulnerable to a terrorist attack.

Two boats sailed into the northwestern port with the plutonium at around dawn after a more than two-week journey from Charleston in the United States. The cargo was expected to be unloaded in the next few hours.

The plutonium shipment is part of a post-Cold War agreement between the United States and Russia to get rid of plutonium from excess nuclear warheads.

Protesters from the environmental group Greenpeace have been barred from going within 100 meters of the shipment, but they watched the vessels from a distance in several small boats. Any protester who goes nearer faces a $92,280 fine.

The plutonium will be taken under armed guard to a nearby reprocessing plant in the La Hague peninsula in northwestern France and will then be driven nearly 660 miles to a factory in southeastern France for recycling.

Greenpeace says the transport could be attacked by nuclear terrorists. French state-owned nuclear energy firm Areva, which is being paid to reprocess the plutonium, says it is safe.

Cogema will recycle the plutonium into nuclear fuel at its Cadarache and Marcoule plants in southeastern France and ship it back to the United States which plans to use it in an electricity-generating reactor.

This is part of the U.S. Department of Energy's controversial program to turn plutonium from the "excess" nuclear warheads into mixed-oxide (MOX) plutonium-uranium enriched fuel.

Greenpeace protesters bolted a heavy truck to the road leading to La Hague Tuesday and chained themselves to the vehicle to try to stop the delivery of the plutonium.

Police used chain cutters to cut free the protesters and dragged them away. They later removed the truck.