24 December LA Times - On the Trail of the Taliban's Support by Paul Watson.

... "A hundred armed Taliban men passed through the Pakistani border with their equipment, and with their rocket-propelled grenade launchers," said Qasim Khail, commander of the Afghan border police's 2nd Brigade, which guards the post here. "And they retreated the same way. There are only two escape routes out of here, and both of them end at a Pakistani border post."

Confidential documents obtained by The Times show that for at least two years, U.S. military intelligence agencies have warned American commanders that Taliban militants were arming and training in Pakistan, then slipping into Afghanistan with the help of Pakistani border control officers...