President Bush called the attack that killed former Pakistan Prime Minister Benazir Bhutto "cowardly" and called for those responsible for the assassination to face justice.
Speaking from his ranch in Crawford, Texas, Bush told reporters today, "The United States strongly condemns this cowardly act by murderous extremists who are trying to undermine Pakistan's democracy. Those who committed this crime must be brought to justice."
Bush praised Bhutto's past leadership of her country and acknowledged that despite the danger posed to her life after her return to Pakistan from exile earlier this fall, "she refused to allow assassins to dictate the course of her country."
"We stand with the people of Pakistan in their struggle against the forces of terror and extremism. We urge them to honor Benazir Bhutto's memory by continuing with the democratic process for which she so bravely gave her life," Bush said.
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Bush also offered his condolences to Bhutto's family, friends and supporters, as well as the families of the others killed in the attack. The White House said Bush called Pakistan's president, Pervez Musharraf, at approximately 1:15 p.m. ET.
According to White House spokesman Scott Stanzel, Bush first learned of the attack at his regular morning briefing, which began at 8:30 a.m. ET.
At the State Department today, spokesman Tom Casey read a statement from Secretary of State Condoleezza Rice at a press briefing. Rice extended her sympathy and condolences on the "tragic death" of Bhutto and said, "We condemn in the strongest possible terms, this cowardly and murderous attack. Ms. Bhutto's passing is a great loss for Pakistan."
"I knew her as a woman of great courage and had been impressed by her dedication and commitment to democracy and the future of Pakistan itself," Rice's statement continued.
Casey confirmed that Rice called Bhutto's husband after the attack to personally offer her condolences.
As for the situation in Pakistan, the statement continued, "The deadly results of this attack will no doubt test the will and patience of the people of Pakistan. We urge the Pakistani people, political leaders, and civil society to maintain calm, and to work together to build a more moderate, peaceful and democratic future."
The State Department has been heavily involved in attempts to keep the situation in Pakistan calm over the last month, and to work with Musharraf, whom the Bush administration views as a key political ally for combating terrorism and maintaining political stability.
Bhutto's death is a blow to the U.S. administration's plan to bring her back to Pakistan where there could be a power-sharing agreement with Musharraf, who has lost popular support in that country.
The former prime minister was campaigning intensely for parliamentary elections to be held Jan. 8. Polls had shown her party in the lead.
One of Bhutto's key campaign themes was fighting terrorism in Pakistan, and fighting al Qaeda. She had accused Musharraf of not doing enough to combat the problem.
ABC News' Jonathan Karl visited Islamabad earlier this year with Vice President Dick Cheney. On that trip, senior officials spoke about their fears that Pakistan could turn to what one official called "the dark side." Bhutto's assassination will not likely help in avoiding that turn.
"Whoever perpetuated this violence was someone who was an enemy of democracy," Stanzel said at an afternoon press briefing. "But it's too early at this point to say that from our perspective. Understand there may be claims of responsibility out there, but I'm sure the Pakistani authorities will be looking into the matter."
When asked if the Bush administration has confidence in Musharraf's government to conduct a proper investigation of the assassination, Stanzel said, "I think it's important to have a thorough investigation of that. We expect that that will happen. And like I said, I think we're willing to work with our allies in Pakistan to make sure that does happen."
ABC News' Jonathan Karl, Jon Garcia and Theresa Cook contributed to this report.