Breaking ranks with the Bush administration, a top Republican lawmaker, who was scheduled to meet slain former Pakistani premier Benazir Bhutto [Images] the day she was killed, has urged the United Nations Secretary-General Ban Ki-moon to appoint an investigating commission into her assassination.

Senator Arlen Specter of Pennsylvania and Congressman Patrick Kennedy were in Pakistan at the time of the Bhutto's assassination and were scheduled to meet both the President Pervez Musharraf [Images] and Bhutto.

According to Bhutto's Pakistan People's Party officials she was scheduled to meet the US lawmakers to hand over a confidential report on the diversion of US aid for fighting militants by Pakistan's Inter-Services Intelligence to rig the upcoming parliamentary polls.

In his letter to the UN secretary general, Senator Specter, sitting on the Senate Judiciary Committee, suggested that the Scotland Yard or the Federal Bureau of Investigation can undertake an independent investigation on behalf of the world body.

"In light of the uncertainty on who assassinated former Pakistan prime minister Benazir Bhutto and the impact of her assassination on the pending Pakistani elections, I urge the United Nations, either alone or in conjunction with the Musharraf government of Pakistan, to appoint an investigating commission," Specter wrote.

"Since President Musharraf has already suggested an international investigation, joint action by the UN would be consistent with Pakistani sovereignty. Even without the voluntary joinder of the Musharraf government, it is obvious that a UN investigation would have greater public credibility," Specter said.