The duo intended to frighten Davis because he crossed a "red line," The Washington Post quoted the official, as saying, without defining the line he mentioned.
Both Pakistan military's Inter-Services Intelligence Service (ISI) and the Interior Ministry's Intelligence Bureau regularly use motorcycle tails to track the movement of US officials, another Pakistani official was quoted, as saying.
The report said the Pakistani media has also suggested that Davis is being held hostage to a death case brought in New York by family members of four Americans killed in the 2008 terrorist attack in Mumbai, India.
US and Indian officials have blamed the attack on Pakistani organization Lashkar-i-Taiba that has long-standing ties to the ISI, said the report, noting that four senior ISI officials- including the organization's director Lt. Gen. Ahmed Shuja Pasha- have been called as witnesses in the case.
However, during a press briefing at the US Department of State, Assistant Secretary of State for Public Affairs Philip J. Crowley insisted that the killed men were robbers.
When asked that 'several Pakistani officials now who are challenging the US Government's take on what exactly happened, saying that the two individuals who were pursuing him were not robbers, were actually members of the ISI. Do you have anything to say about that? Do you stand by your version of events?, Crowley replied in the affirmative.
On being asked about it in detail, Crowley said: "Again we have heard those media stories. I don't think that we have information on that."
When inquired whether he did not have any information to support that, or he did not find them credible, he replied: "We don't find them credible."