While the military provides few specifics of its supply operation, observers believe most of the supplies travel through the Khyber Pass, says Reuters.
The U.S. military and NATO have not given details of the supplies they get via Pakistan or a breakdown of how much comes on the two routes. The U.S. Defense Department says the U.S. military sends 75 percent of supplies for the Afghan war through or over Pakistan, including 40 percent of fuel.
Pakistani customs officials say under normal circumstances about 300 trucks with Western force supplies travel through the Khyber Pass crossing at Torkham every day, compared with about 100 through the Chaman crossing.
With the US planning to expand its Afghan operations, Tuesday's bridge attack highlights the need for secure supply routes. US planners say they are actively looking for routes that avoid Pakistan's volatile border areas.
There are 36,000 American soldiers currently stationed in Afghanistan, where they are training Afghan security forces and doing battle with a Taliban insurgency against the government of US ally Hamid Karzai.