More foreigners are infiltrating Afghanistan because of a recruitment drive by al-Qaeda as well as a burgeoning insurgency that has made movement easier across the border from Pakistan, U.S. officials, militants and experts say. For the past two months, Afghanistan has overtaken Iraq in deaths of U.S. and allied troops, and nine American soldiers were killed at a remote base in Kunar province Sunday in the deadliest attack in years.

Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, warned during a visit to Kabul this month about an increase in foreign fighters crossing into Afghanistan from Pakistan, where a new government is trying to negotiate with militants.

Two U.S. officials, who spoke on condition of anonymity because of the sensitivity of the information, told The Associated Press that the U.S. is closely monitoring the flow of foreign fighters into both Afghanistan and Pakistan.

Jihadist websites from Chechnya to Turkey to the Arab world featured recruitment ads as early as 2007 calling on the 'Lions of Islam' to fight in Afghanistan, said Brian Glyn Williams, associate professor of Islamic history at the University of Massachusetts. Williams has tracked the movement of jihadis for the U.S. military's Combating Terrorism Center at West Point. ...