ISLAMABAD, Pakistan - President Bush reached out yesterday to support longtime ally Pervez Musharraf, calling the embattled Pakistani president to assure him of continued U.S. backing.

Musharraf's demise is considered almost a foregone conclusion in Pakistan, but Bush's intervention appeared to be a powerful signal that Washington would not welcome the Pakistani leader's exit.

"The president reiterated the United States' strong support for Pakistan, and he indicated he looked forward to President Musharraf's continuing role in further strengthening U.S.-Pakistani relations," White House spokeswoman Dana Perino said in Washington.

Pakistan is abuzz with speculation that Musharraf's attempts to cling to power have collapsed. His enemies have stepped up their attacks, and even his supposed allies have gone silent.

His weakened status also may have emboldened disgraced nuclear scientist Abdul Qadeer Khan - held under house arrest by Musharraf - to assert in an interview published yesterday that he was coerced into confessing that he had passed nuclear secrets to North Korea, Libya and Iran.

Khan was detained in 2004 after he had admitted passing on nuclear technology to other countries. But in an interview with the British newspaper the Guardian, Khan said of his confession: "It was not of my own free will. It was handed into my hand."

Experts suspect that Khan was persuaded to make the confession to conceal government involvement in the trafficking. Khan enjoys hero status in Pakistan.

Talk of Musharraf's imminent departure has reached fever pitch. Persistent speculation of a rift between the president and army chief Ashfaq Kayani forced Musharraf to publicly deny it.

"This [Bush call] is a shoring up, an effort to demonstrate continued support," said Dan Markey, a former State Department official now at the Council on Foreign Relations, a nonpartisan research center in Washington.

Pakistan's fragile coalition government, which came to power after elections in February, has taken an increasingly hard line against Musharraf, who rose to power in a 1999 military coup.