American officials insist he is entitled to diplomatic immunity and that he be released immediately.
Davis has been held for almost a month in a Lahore prison while a court decides his status.
The case has provoked a surge in anti-American hostility and spawned a wave of conspiracy theories.
Many Pakistanis have questioned whether Davis was really the victim of an attempted robbery – as he told police – and exactly why he was driving around Lahore with a Glock handgun in a rented car.
This week it emerged that he was employed by the CIA and that he was engaged in an undercover operation.
