ISLAMABAD/WASHINGTON, August 17: The United States has begun evacuating all its citizens from Pakistan, save essential diplomatic staff, following the arrest in Karachi of a suspect in the Nairobi bombings and the fear of reprisals against American targets.Mohommad Sadiq, 34, was arrested when he arrived in Karachi from Nairobi on the day of the bombing. He was held when it was found his face did not match the picture in his Yemeni passport.Sadiq reportedly confessedproudly and calmly according to one accountto having provided the technical, engineering and logistical support for the August 7 bombing which killed 247 people including 12 Americans.He also acknowledged being part of a team of seven militants trained and financed by the Afghan-based Osama Bin Laden, the Saudi millionaire-terrorist at whom the needle of suspicion for this attack has been hovering. Some reports said all seven returned to Karachi along with Sadiq and six of them managed to slip through airport inspections.Sadiq, aPalestinian engineer, was not booked in a fake passport case and instead after initial investigations, the US embassy in Islamabad was informed of his presence, says The News, a leading English language daily from Islamabad.The FBI was quick in sending a special plane to Karachi where US agents during a brief stay on Thursday were handed the Palestinian suspect, who was immediately taken to an unknown destination, says the paper.Meanwhile, several American families have begun arriving at Islamabad and Karachi airports on their way out. US companies said they would ask their American staff to go on leave.In the past, each arrest of a terrorist in Pakistan has been followed by retaliation against soft US targets that country. Four oil company executives were gunned down in Karachi two days after the conviction of Mir Aimal Kansi in November 1997 of killing two CIA employees. In March 1995, a month after the capture of World Trade Center bombing suspect Ramzi Yousef, gunmen ambushed a US consulatevan and killed two US government employees.``We have informed the Pakistani government of our regret in having to take this action,'' a State Department official said.Sadiq is said to have told his interrogators that his group would be personally greeted by the Saudi millionaire Osama Bin Laden for the task. ``Osama Bin Laden is our supreme commander. We have shown our determination to meet our pledge to the Muslim world.''The newspaper report also said that Pakistan was currently preparing to assist the United States in trying to nab Osama Bin Laden from Afghanistan in an operation at a later date.While Pakistani officials are claiming that Sadiq had come clean, US officials in Washington said the suspect had not admitted his involvement to American interrogators. But Washington is taking no chances. The State Department has released a worldwide caution to American travelers with an accompanying statement specifically warning against ``all travel to Pakistan.''``American citizens currently inPakistan are urged to consider carefully their security situation and, in light of the ordered departure of all non-emergency official personnel, to consider seriously departing Pakistan,'' the warning said.Despite the veneer of cooperation, the US and Pakistan face several awkward problems, especially in case the US wants to go after Bin Laden. The Saudi national lives in Afghanistan under the patronage of the Taliban government, which in turn is backed and recognised by Pakistan.