Pakistan’s refusal to open up key NATO supply routes into Afghanistan is costing the U.S. an additional $100 million every month to move supplies and equipment to allied troops via Central Asia in the north.

Defense Secretary Leon Panetta made the estimate during testimony before Congress.

Following the accidental killing of 24 Pakistani troops by U.S. missiles last November, Islamabad has closed the transport routes.

Negotiations between the U.S. and Pakistan to reopen the roads have been deadlocked, reportedly because the Pakistanis are demanding an exorbitant charge.