The two-vehicle convoy, which were travelling from University Town neighbourhood to the consulate, were hit by a suicide bomber on a motorcycle, US Embassy spokesman Alberto Rodriguez told PTI.
"Two US government employees were slightly injured by the blast. There were no deaths or serious injuries," Rodriguez said.
An armoured SUV bore the brunt of the blast and rammed into an electricity pylon.
"The other vehicle evacuated the occupants of the damaged car," Rodriguez said.
Police officials said a passer-by was killed and over 10 others injured by the powerful blast. Reports said the dead passer-by was on a motorcycle though it could not immediately be ascertained if he was the suicide bomber.
TV news channels reported that the banned Tehrik-e-Taliban Pakistan claimed responsibility for the attack, the first targeting American nationals since Osama bin Laden was killed in a US raid in the garrison city of Abbottabad on May 2.
Taliban spokesman Ahsanullah Ahsan told the media that his group would target the diplomatic staff of all NATO nations.
He said Pakistan was the Taliban's "first target" and the US the second. The Taliban had earlier warned they would avenge bin Laden''s death with attacks on American and Pakistani targets.
On May 13, two suicide bombers struck a paramilitary training facility in the northwestern town of Shabqadar, killing nearly 90 people, including scores of recruits of the Frontier Constabulary.