The US urged Pakistan to clear up how opposition leader Benazir Bhutto was assassinated and conceded that crucial January 8 elections may be postponed after her death.
Pakistani officials gave shifting versions of Bhutto's death after a campaign rally on Thursday. Interior Ministry officials said she broke her skull on the sunroof of her vehicle after a bomb went off. Earlier, doctors said she died from a bullet to the neck.
"Certainly, we expect that there will be a full investigation of this," Tom Casey, a US state department spokesman, said on Friday.
"And I think it's important for Pakistan that everyone feel that there is closure and that there is an understanding of the exact circumstances surrounding her assassination, as well as who is responsible for it," he said.
Bhutto, a former two-time prime minister who returned from self-imposed exile in October, was the linchpin of a US strategy to promote democracy and fight Islamic extremism in her nuclear-armed country.
US Secretary of State Condoleezza Rice said Friday "it's just very important that the democratic process go forward" in Pakistan, but sidestepped the question of keeping to the planned election date.
Signing a book of condolences at the Pakistani embassy in Washington, she called Bhutto "a champion of democracy" and her death a tragedy.
Casey said the US will continue to work with other Pakistani opposition leaders and President Pervez Musharraf, the increasingly unpopular military ruler who is a critical ally in US efforts to fight terrorism.
But the state department sought to dispel questions whether the Bush administration has depended too much on Musharraf.
"US policy is not to support any individuals in this," Casey said. "What we want to see happen is the development of a democratic system in Pakistan."
He conceded that next month's election may be delayed - something he said Thursday would be a victory for "extremists".
On Friday, he said he "wasn't trying to convey that there's something magic about January 8."
"If political parties and actors in the country come to some different conclusion, then certainly we'll take a look at it then," he said.
Pakistani caretaker Prime Minister Mohammedmian Soomro said on Friday that the government was considering postponing elections and would consult the country's main opposition parties.