WASHINGTON: President Barack Obama urged Pakistan Tuesday to free a detained US official, while insisting that he was not "callous" about the deadly shooting that led to the US employee's arrest.

In his first public remarks on a case that has cast a chill over an already uneasy partnership, Obama said that detained official Raymond Davis enjoyed diplomatic immunity under the Vienna Conventions.

"We expect Pakistan... to abide by the same convention," Obama told a news conference.

"We're going to be continuing to work with the Pakistani government to get this person released," he said.

"Obviously, we're concerned about the loss of life. We're not callous about that, but there is a broader principle at stake," Obama said.

Davis insists he acted in self-defense when he shot dead two Pakistanis in the eastern city of Lahore on January 27. Another Pakistani died when struck by a US diplomatic vehicle that came to Davis' assistance.

But many Pakistanis have been suspicious about Davis, who was arrested with loaded weapons and a GPS satellite tracking device. US authorities have been vague as to his role in Pakistan.

Obama said that diplomatic immunity was critical because otherwise diplomats who "deliver to tough messages to countries where we disagree with them" will "start being vulnerable to prosecution locally."

"That's untenable. It means they can't do their job," Obama said.

The United States has put heated pressure on Pakistan's weak government to free Davis, triggering a new flare-up in anti-US sentiment in the frontline nation in the US-led campaign against Islamic extremism.

The United States has put off three-way talks with Pakistan and Afghanistan that were due to be held next week.