Pentagon says "fundamental strategy" in Afghanistan is sound Since then, NATO advisers in Kabul have been restricted to communicating with Afghan government ministries by telephone and e-mail in an attempt to avoid further attacks on U.S. and NATO forces by their ostensible allies within the Afghan government. U.S. officials said the decision by Marine Gen. John Allen, the top U.S. and NATO commander, to pull NATO advisers from the ministries was temporary but that no date has been set for them to return to work. The killing of the two U.S. 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. More than two dozen U.S. and NATO troops have been killed by Afghans wearing official police or army uniforms since the start of last year. The fratricidal killings 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 the war by 2014. On Monday, Pentagon officials sought to play down the effects of those killings as well as the violent protests which erupted across Afghanistan since Tuesday, when Afghans witnessed U.S. military personnel burning copies of the Koran at Bagram air base. U.S. officials have said the burning of the Islamic holy book and other religious texts was accidental, but public apologies by President Obama and other leaders have not ended the fallout. "Anyone who believes they can weaken our resolve through these cowardly attacks is severely mistaken," George Little, the Pentagon press secretary, 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 in Afghanistan. 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 there were no coalition service members killed in the attack, in which the bomber detonated a car laden with explosives at the main entrance of the base. U.S. and Afghan officials said they were still seeking to identify the assailant who fatally shot two U.S. officers at close range Saturday in a supposedly secure area of the Afghan Interior Ministry, one of the most closely guarded buildings in Kabul. The gunman fled and remains at large; investigators are trying to determine whether other Afghans working in the ministry enabled or assisted in 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 NATO spokesman in Kabul. The officers killed in the attack have been identified as Army Maj. Robert Marchetti of Baltimore, a member of the Maryland Army National Guard, and Air Force Lt. Col. John Loftis, 44, of Paducah, Ky., a member of the 886th Air Expeditionary Squadron. Kirby said a joint NATO and Afghan investigation into the Koran burnings was still unfinished. 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.