Defense Secretary Robert Gates on Wednesday expressed "personal regret" for recent U.S. airstrikes that killed Afghan civilians, and pledged more accurate targeting in future.

After meeting with Afghan President Hamid Karzai and other senior government officials, Gates said at a news conference, "As I told them, I offer all Afghans my sincere condolences and personal regret for the recent loss of innocent life as a result of coalition airstrikes."

Gates said the U.S. military takes extraordinary precautions to avoid civilian casualties, but added, "It is clear that we have to work even harder." He told Afghan officials that he would be discussing the issue with American commanders and pilots on Wednesday.

Gen. David McKiernan, the commander of international forces in Afghanistan, said earlier that a shortage of U.S. troops in Afghanistan is forcing commanders to rely more on air combat, which can cause more civilian deaths. The attacks that have angered and embarrassed the U.S.-backed Afghan government.