Obama sees deaths of soldiers in NATO air strike as tragedy

White House spokesman Jay Carney said Obama believed Saturday's attack, which threw strained relations into fresh turmoil, was "a tragedy," adding that "we mourn those brave Pakistani service members that lost their lives."

"We take this matter very seriously," said Carney, adding that two separate probes -- one by NATO's International Security Assistance Force (ISAF) in Afghanistan, the other by US Central Command -- would examine what took place.

"As for our relationship with Pakistan, it continues to be an important cooperative relationship that is also very complicated," Carney said.

"It is very much in America's national security interest to maintain a cooperative relationship with Pakistan because we have shared interests in the fight against terrorism."

Pakistan earlier vowed no more "business as usual" with the United States, but stopped short of threatening to break the troubled alliance altogether.

NATO and the United States are trying to limit fallout from the attack, but Islamabad has shut vital supply routes to the 140,000 foreign troops serving in Afghanistan.

US State Department deputy spokesman Mark Toner said "we're concerned about the impact of this incident on our relations with Pakistan," which he said had yielded results in fighting militancy.

He also said "this is a relationship that has weathered significant setbacks.... I don't think anyone can deny that.

"But it's one that's also, through every challenge and through every setback, has moved forward because it's so vitally important to both our countries."

Toner also said the United States understood that Islamabad was "reconsidering" whether to attend the international conference in Bonn.

He urged Islamabad to attend, saying it was "very much in the interests of Pakistan."

Copyright AFP (Agence France-Presse), 2011