Washington insists the detained American has diplomatic immunity and killed the Pakistanis in self-defense as they tried to rob him at gunpoint. It says the man's detention is illegal under international agreements covering diplomatic ties.

Pakistani leaders, facing a groundswell of popular anger triggered by the incident, have avoided definitive statements on the status of the American, whom they have named as Raymond Davis. Davis's next court appearance is set for Feb. 11.

Two senior U.S. officials told The Associated Press on Monday that talks involving Afghanistan, Pakistan and the U.S. set for Feb. 24 in Washington are now in doubt because of the spat. The officials spoke on condition of anonymity because they are not authorized to release the information publicly.

The talks are supposed to be held at the ministerial level, meaning U.S. Secretary of State Hillary Rodham Clinton and Pakistani Foreign Secretary Shah Mahmood Qureshi would participate. It's possible that they could simply be downgraded to included just lower-level officials.

Pakistani Foreign Ministry spokesman Abdul Basit said the two countries must not lose sight of the strategic imperatives of their relationship.

"Our relations are mature enough to navigate through difficulties," he wrote in a text message.

U.S. Ambassador to Pakistan Cameron Munter met with Pakistani President Asif Ali Zardari on Monday and pressed him to release Davis. That meeting and recent U.S. press statements have indicated growing frustration with an ally considered key to ending the conflict in Afghanistan.