The intelligence was also shared with the Pakistani government, the officials said.
Much of what was passed on dealt with general threats from Taliban extremists and al-Qaida sympathizers and "was not actionable information."
The officials said Bhutto and her aides were concerned, particularly after the October attack, but were adamant that in the absence of a specific and credible threat there would be few, if any, changes to her campaign schedule ahead of parliamentary elections.
"She knew people were trying to assassinate her," said an intelligence official. "We don't hold information back on possible attacks on foreign leaders and foreign countries." The official added, however, that while the U.S. could share the information, "it's up to (the recipient) how they want to take action."
"We gave them a steady stream of intelligence," one official said.
The officials spoke to AP on condition of anonymity due to the sensitivity of the matter and amid widespread disbelief over the Pakistani government's assertion that Bhutto died not from bullet or shrapnel wounds but from injuries sustained while hitting her head on her vehicle's sunroof during Thursday's attack by a suicide bomber and gunman.
The dispute over the government's explanation of how she died intensified after a medical report didn't state what had caused her injuries and a video obtained by Britain's Channel 4 television showed a man firing a pistol at Bhutto from just feet away as she poked her head out of the sunroof. In the footage, her hair and shawl jerk upward and she falls into the vehicle just before an explosion. No police are seen trying to push the crowd away.
The Bush administration has quietly joined calls for Pakistan to allow international experts to join the probe into Bhutto's Dec. 27 slaying. The officials said they expected an announcement soon that investigators from Britain's Scotland Yard would be asked to play a significant role. Any U.S. involvement would be limited and low-key, they said.
In the meetings with U.S. officials, Bhutto aides did not ask the United States to help protect her but did inquire about the feasibility of hiring private U.S. or British bodyguards, an idea discouraged by the Americans who argued that a noticeable Western security detail would increase the threat and might become a target itself, the officials said.
Instead, the U.S. diplomats recommended as many as five reputable local Pakistani and regional firms that could be contracted to supplement Bhutto's security and urged the party to limit the size, scope and type of her public appearances, upgrade armoring on vehicles in which she might travel and require her to wear protective clothing, the officials said.
However, there was no indication that Bhutto's team including her husband, Asif Ali Zardari, who attended at least one of the meetings had followed through on the most critical of the recommendations, including the hiring of private guards and reducing her visibility in large crowds like the one in Rawalpindi where she was killed.
The officials said Zardari rejected using private Pakistani security companies due to fears they might be infiltrated by extremists even though several of the recommended companies have international components and are used by Western embassies to protect personnel.
Anne Tyrell, a spokeswoman for the private U.S. security company Blackwater Worldwide, known for its operations in Iraq, said her company had been approached about possibly providing protection for Bhutto, "but unfortunately, an agreement was never reached."
While Bhutto's staff did take some steps to improve the safety of the party's vehicles, the officials expressed surprise that the car in which she was riding when attacked had a sunroof and stressed that they would have strongly advised her against popping her head out of it in the presence of large numbers of people.
In addition to advising Bhutto's aides, as they worked to forge a political reconciliation and possible power-sharing deal between the opposition leader and Musharraf, the U.S. diplomats made numerous appeals to the Pakistani government to grant requests from her party to ensure Bhutto's safety, the officials said.
But some requests, such as those for advanced technology and massive police presences in outlying towns, either could not be met or were deemed unreasonable by the government, a position the United States reluctantly conceded, the officials said.
The State Department, meanwhile, angrily denied suggestions that U.S. officials had ignored or minimized the threat to Bhutto even as they were encouraging reconciliation between her and Pakistani President Pervez Musharraf.
"It is simply untrue and I simply do not understand why anyone, anywhere would assert that the United States did not have concerns, minimized those concerns, or was not very active in trying to ensure that she was provided with whatever kind of security support she required," deputy spokesman Tom Casey told reporters.
"We discussed those concerns regularly both with her and officials from her party and with President Musharraf and with his government," he said. "We always, in every instance, took those concerns seriously. We were very active in trying to ensure that any information we had that was relevant to her situation was passed on to her as well as those responsible for her security."
Associated Press writer Eileen Sullivan contributed to this report.
