Washington - The Pentagon said Monday that it will not change its "fundamental strategy" in Afghanistan despite a week of crises that have worsened the strained partnership between the Afghan government and U.S. and NATO forces.

U.S. officials acknowledged that tensions remain high in Kabul and that distrust has not dissipated since last weekend's killing of two U.S. military officers inside the Afghan Interior Ministry, apparently by a rogue Afghan security officer.

The killings, which prompted Marine Gen. John Allen, the top U.S. and NATO commander, to pull service members from the ministries, has forced NATO advisers in Kabul to limit communication with Afghan government ministries to telephone and e-mail. U.S. officials said Monday that, although the measure is temporary, no date has been set for the advisers to return to work.

The deaths of the two American officers on Saturday followed a similar incident two days earlier in which two U.S. troops were gunned down by an Afghan soldier in Nangahar province. At least 36 U.S. and NATO troops have been killed by Afghans wearing official police or army uniforms since the start of last year, according to a review of military casualty reports.

The fratricidal attacks have fueled suspicions at a vulnerable time for the U.S. military and NATO, which are trying to partner more closely with Afghan security forces so they can take over responsibility for the war against the Taliban and other insurgents. Former U.S. officials and analysts have said the consequences of an erosion of confidence in the U.S.-Afghan partnership could be devastating for NATO's strategy to end combat operations by the end of 2014.

On Monday, Pentagon officials sought to play down the effects of those killings as well as the violent protests that erupted across Afghanistan beginning last week, when Afghans witnessed U.S. military personnel burning copies of the Koran at Bagram Air Base. U.S. officials have said that the burning of the Islamic holy book and other religious texts was accidental, but public apologies by President Barack Obama and other leaders have not ended the fallout.

"Anyone who believes they can weaken our resolve through these cowardly attacks is severely mistaken," Pentagon press secretary George Little said at a news conference. "There is much at stake in Afghanistan, and our commitment to our mission and our strategy will not waver."

Still, violence has continued to spread. On Monday, nine people were killed in a suicide strike aimed at a NATO base in the eastern city of Jalalabad. A spokesman for NATO-led coalition forces said that no coalition service members were killed in the attack, in which a bomber detonated a car laden with explosives at the main entrance of the base.

Anthony H. Cordesman, a military analyst at the Center for Strategic and International Studies who has served as a consultant for the Pentagon, said the recent crises are only symptomatic of deeper problems undercutting the Obama administration's war strategy.

Among them, he said, are the persistence of insurgent networks, the existence of Taliban sanctuaries across the border in Pakistan, corruption within the Afghan government, and poor coordination among NATO allies.

"It has been a truly grim week and one where these events raise questions about U.S. strategy and the value of continuing with the current approach to the war," Cordesman wrote Monday in an online commentary. "The reality, however, is that the strategy . . . has been dying for a long time."

U.S. and Afghan officials said they are still trying to identify the assailant who fatally shot two U.S. officers at close range Saturday in the Afghan Interior Ministry, one of the most closely guarded buildings in Kabul. Investigators are trying to determine whether other Afghans working in the ministry enabled his escape.

"We don't know all the facts surrounding how this individual got into this space and, frankly, was able to get out as quickly, and apparently as easily, as he did," said Navy Capt. John Kirby, a U.S. military spokesman in Kabul.

The officers killed in the attack have been identified as Army Maj. Robert J. Marchanti II, 48, of Baltimore, a member of the Maryland Army National Guard, and Air Force Lt. Col. John D. Loftis, 44, of Paducah, Ky., a member of the 866th Air Expeditionary Squadron.

Kirby said a joint NATO and Afghan investigation of the Koran burnings is continuing. NATO officials had said they would provide a public accounting last week for how the incident occurred, but did not explain why there has been a delay.

Special correspondent Sayed Salahuddin in Kabul and staff writer Susan Svrluga and staff researcher Julie Tate in Washington contributed to this report.