Davis, who is being held in a Lahore jail amid a tense US-Pakistan diplomatic dispute over whether he has diplomatic immunity, was working as a "protective officer," the sources said.Davis' duties as a protective officer -- essentially a bodyguard -- were to provide physical security to US Embassy and consular officers, as well as visiting American dignitaries, US officials who declined to be identified told Reuters.The officials strongly denied news reports alleging Davis was part of a covert CIA-led team of operatives conducting surveillance on militant groups in Pakistan. The officials insisted Davis was not part of any undercover operations team.Two US sources familiar with the matter confirmed to Reuters that Davis, a former member of the US Special Forces, had previously worked on contract as a security officer for Xe Services, a controversial private contractor formerly known as Blackwater.Asked during a conference call with reporters about a link between Davis and the CIA, US State Department spokesman P.J. Crowley declined to comment."We will not comment on his particular activity in Pakistan other than to say he is a member of the administrative and technical staff of the embassy and has diplomatic immunity.""Certain Pakistani officials have proclaimed his guilt before any legal proceeding has reached a conclusion. That's not the way the rule of law should work in that country or elsewhere," a US official said."Davis is a protective officer, someone who provides security to US officials in Pakistan. Rumors to the contrary are simply wrong," the official added.Earlier today, AFP quoted a Pakistani intelligence official as saying that Davis is an undercover CIA contractor."It is beyond any shadow of a doubt that he was working for CIA," an official from Pakistan's Inter-Services Intelligence (ISI) agency told AFP on condition of anonymity."He's on contract. He's not a regular CIA guy, but he's working for CIA. That's confirmed," the Pakistani official said.Pakistan's powerful intelligence services and military have been angered by accusations that they support Taliban and al Qaeda-linked networks fighting US troops in Afghanistan, and need to do more to eliminate militants.Few in Pakistan believe Davis, who reportedly worked for a security contractor and had a background in US Special Forces, is a regular diplomat Police told AFP they recovered a Glock pistol, four loaded magazines, a GPS navigation system and a small telescope from his car, after the shooting on a busy street in Lahore on January 27.A third Pakistani was struck down and killed by a US diplomatic vehicle that came to Davis's assistance. US officials denied Pakistan access to the vehicle and the occupants are widely believed to have left the country.Washington insists that Raymond Davis, who says he acted in self-defence, is a member of its Islamabad embassy's "administrative and technical staff" who has diplomatic immunity and should be released immediately.But the unpopular government in Pakistan is under huge pressure from the political opposition not to cave in to US demands, with analysts even warning that the case could bring down the ruling Pakistan Peoples Party (PPP).Washington has postponed a round of talks with Afghanistan and Pakistan, but Islamabad has said the matter is before the courts , although one compromise would be for the families to pardon Davis, in keeping with Islamic law.Meanwhile, Prime Minister Yousaf Raza Gilani told the lower house on Monday that he was confident "that both the Pakistani and the US governments will not allow the Davis case to come in the way of mutually beneficial partnership".He said Pakistan was mindful of its international obligations under the Vienna Convention and other agreements.But he added: "I want to assure this house and the nation that my government will not compromise on Pakistan's sovereignty and dignity. We are a responsible government and conscious of the sentiments of our people."On Monday, a judge at the Lahore High Court ordered the government to appear on March 14 to respond to private petitions related to Davis' incarceration, the law on diplomatic privileges.The court last week deferred any judgement on whether Davis has diplomatic immunity and gave the foreign ministry until March 14 to determine his status.US Senator John Kerry visited Pakistan last week to express regret and say Davis would face a criminal investigation at home, but hopes for a swift resolution now appear unlikely.Local analysts suggested Pakistani intelligence had deliberately decided to complicate the case in order to put pressure on the government and the United States, with whom relations have been troubled over the war in Afghanistan."This would be seen as a kind of deliberate attempt to make the situation more difficult and complex to handle, and this provides additional material to the Islamic groups to adopt a hardline stance," said analyst Hasan Askari."These (intelligence) groups are not happy with the way America was building pressure on Pakistan on the war on terrorism. "If it goes to the street and massive agitation, all political parties will find it a good opportunity to knock the PPP out of power," he said.So sensitive is the case that Fauzia Wahab, spokeswoman for the ruling party, was forced to resign after saying that diplomats have immunity and that Davis had an "official" visa.The PPP has also ditched former foreign minister Shah Mehmood Qureshi in a recent cabinet reshuffle.Qureshi, who was still in his post at the time of the shootings, said last week that in his view Davis did not have full diplomatic immunity.The Pakistani intelligence official said the Davis case had soured relations with the Central Intelligence Agency."Our relations with the CIA are now sort of pretty dicey. It has affected our relationship," the official told AFP.