U.S. Senator John Kerry said today his country was "deeply sorry" over the killing in late January of two Pakistanis by a U.S. consular official.
Kerry said he had come to Pakistan to express regret for the deaths and the sorrow of the American people.
Kerry is the chairman of the Senate Foreign Relations Committee.
U.S.-Pakistani relations were strained by the incident, in which a consular official shot dead two Pakistani men who he said were trying to rob him.
The man is being detained by Pakistani authorities pending an investigation into possible murder charges.
The U.S. has maintained that as a consular official, the man has diplomatic immunity and must be released immediately.
U.S. President Barack Obama today reiterated the U.S. demand that Pakistan respect diplomatic immunity and release the man.