A new international force to battle pirates off the Somali coast is being formed under American command in a bid to focus more military resources to protect one of the world's key shipping lanes, the US Navy said yesterday.

But the new mission, expected to begin operations next week, will have no wider authority to strike at pirate vessels at sea or move against havens on shore. That raises questions whether it can significantly curb pirate flotillas after more than 110 ships were attacked last year.

International efforts to fight piracy have mounted in recent months. More than 20 nations are expected to take part in the new US-led mission.