WASHINGTON  As President Obama vows to “finish the job” in Afghanistan by sending more troops, the Senate Foreign Relations Committee has completed a detailed look back at a crucial failure early in the battle against Al Qaeda: the escape of Osama bin Laden from American forces in the Afghan mountains of Tora Bora in December 2001.

“Removing the Al Qaeda leader from the battlefield eight years ago would not have eliminated the worldwide extremist threat,” the committee’s report concludes. “But the decisions that opened the door for his escape to Pakistan allowed bin Laden to emerge as a potent symbolic figure who continues to attract a steady flow of money and inspire fanatics worldwide.”

The report, based in part on a little-noticed 2007 history of the Tora Bora episode by the military’s Special Operations Command, asserts that the consequences of not sending American troops in 2001 to block Mr. bin Laden’s escape into Pakistan are still being felt.

The report blames the lapse for “laying the foundation for today’s protracted Afghan insurgency and inflaming the internal strife now endangering Pakistan.”