U.S. President George W. Bush lamented the withdrawal from Afghanistan of the Nobel Prize-winning medical relief group Medecins Sans Frontieres, saying Monday its doctors and nurses had performed a valuable function. «I did see that the Doctors Without Borders left,» Bush said, using the group's English name. The group became last week the first major aid agency to pull out of Afghanistan since the U.S. led forces removed the Taliban militia government. «I'm sorry they did, because they were providing an important function for the people who want to live in a free society,» Bush said. The France-based group's principal complaint was that the Afghan government had failed to act on evidence that local warlords were behind the killings this year of five members of its staff. It also said Afghanistan was made much more difficult for aid workers because of the U.S. military's use of humanitarian aid «for political and military motives.» Bush spoke in the Rose Garden on a day when U.S. and allied troops backed by warplanes and helicopters fought dozens of militants in Afghanistan, the biggest border clash along the mountainous Pakistani border in months. «The Taliban still roams in parts of the country, and we're working with the Afghan government to bring them to justice,» Bush said. «These are similar to the killers in Iraq. They'll lurk in shadows and come out and kill indiscriminately.»