In a memoir released on Monday, President Pervez Musharraf recounted how he decided it would have been suicidal to confront a US attack after being threatened by Washington a day after Al-Qaeda's strikes on September 11, 2001.
With the United States demanding Pakistan's help to launch attacks on Al-Qaeda and its Taliban hosts in Afghanistan, Musharraf recalled how the then US Secretary of State Colin Powell had telephoned him with an ultimatum: "You are either with us and against us."
He also wrote that Powell's deputy, Richard Armitage warned Lieutenant-General Mehmood Ahmad, the director-general of the Inter-Services Intelligence, that if Pakistan chose the terrorist's side "then we should be prepared to be bombed back to the Stone Age".
Armitage, who like Powell has left government, on Monday denied using such a threat, after Musharraf first described the exchanges during an interview with CBS's "60 Minutes" last week.
Musharraf's autobiography In the Line of Fire was due to be released in New York on Monday, but some bookshops in Islamabad were already selling copies.
Elaborating on how he decided to take a foreign policy U-turn by dumping support for the Taliban, Musharraf described how he first weighed the option of fighting the United States.
"I war-gamed the United States as an adversary," he wrote, saying he assessed whether Pakistan could withstand the onslaught.
"The answer was no, we could not, on three counts."
Pakistan's military would have been wiped out, its economy couldn't be sustained, and the nation lacked the unity needed for such a confrontation, Musharraf wrote.
Furthermore, Musharraf was worried that if Pakistan did not accede to Washington's demands, the United States would take up an Indian offer to provide bases.
He foresaw India using the opportunity to either launch a limited offensive in the disputed Kashmir region, or more probably New Delhi would work with the United States and the United Nations to turn the present disputed ceasefire line dividing Kashmir into a permanent border.
He also expected the United States would seek to destroy Pakistan's newly developed nuclear weapons. And he feared the infrastructure built since Pakistan's formation in 1947 would be decimated.
Finally, Musharraf said he had to answer whether it was worth Pakistan destroying itself for the sake of the Taliban, though Pakistan had supported the Islamist militia's government.
"The answer was a resounding no," Musharraf concluded.