LONDON (AP) — When facing allegations of U.S. airstrikes killing or injuring civilians in Afghanistan, it is better to apologize first and investigate later, Defense Secretary Robert Gates says.

Gates was in London on Thursday for a NATO meeting that was expected to include a discussion among allied defense ministers of the struggles to turn the tide of insurgent violence in Afghanistan and to train Afghan security forces.

He flew here Wednesday night after spending a day in Afghanistan to discuss with Afghan leaders and American commanders the issue of inadvertent civilian casualties from U.S. airstrikes. At a news conference at the U.S. Embassy in Kabul, Gates said it was time to take a new approach to responding.

“I think the key for us is, in those rare occasions when we do make a mistake, when there is an error, to apologize quickly, to compensate the victims quickly and then carry out the investigation,” Gates told reporters later at Bagram airfield, where he received a briefing from an Air Force general on the rules and restrictions U.S. pilots must follow when providing aerial support to U.S. and allied troops engaged in ground fighting.

In Kabul, Gates offered the people of Afghanistan his “personal regrets” for U.S. airstrikes that have killed civilians and said he would try to improve the accuracy of air warfare, the imperfect fallback for U.S. commanders who say they don’t have enough ground forces for the deepening Afghanistan war.