Pakistan is refusing to take part in a US military investigation of air strikes near the Afghan border that left 24 Pakistani soldiers dead, the Pentagon said Friday.
Pakistan was invited to cooperate in the probe into Saturday's incident, which has enraged Islamabad and plunged US-Pakistani relations into crisis, but officials have declined to do so.
"They have elected to date not to participate, but we would welcome their participation," said Pentagon press secretary George Little.
US officials expected a refusal given the fury in Pakistan following the incident, which led Islamabad to block NATO supply convoys on its border and boycott an international conference on Afghanistan in Bonn set for Monday.
The United States has voiced regret over the strikes but has stopped short of issuing an apology while the American military conducts the investigation.
"It's safe to say that the incident has had a chilling effect on our relationship with the Pakistani military, no question about that," spokesman Captain John Kirby told reporters.
"Both sides deem it to be as serious as it was."
US commanders and intelligence chiefs have long sought to cultivate relations with Pakistan's army, the country's most powerful institution, but the air strikes have caused outrage among the army's junior officers and fed popular resentment of Washington.
The Pakistani army called the strikes a "deliberate act of aggression" but US officials have declined to discuss publicly what transpired at two Pakistani border posts.
Kirby suggested the US military would review its operations and tactics for forces stationed in eastern Afghanistan in the aftermath of the deadly strikes.
"Clearly, an incident like this causes you -- and should cause you -- to take a step back and look at how you're doing things and whether there need to be improvements made or any kind of tactical decisions ...(to) do things a little differently," Kirby said.
"And General (John) Allen is doing that," he said, referring to the top US and NATO commander in Afghanistan.
Asked about reports that Pakistan's army has ordered troops to retaliate immediately if fired on, Kirby said that "every sovereign nation has the right of self-defense and the right to order their troops to defend themselves."
The Wall Street Journal, citing unnamed officials, reported Friday that Pakistan approved the air strikes that killed their troops, unaware that its forces were in the area.
But at the Pentagon news conference, Kirby declined to confirm or deny the report.
