U.S. Defense Secretary Robert Gates warned Monday of "hard fighting" ahead in Afghanistan -- despite recent progress.
Speaking to reporters during his unannounced visit to Kabul, Gates acknowledged "bits and pieces of good news" with the capture of senior Taliban commanders in Pakistan and the takeover of the former Afghan Taliban stronghold of Marjah in Helmand province.
But he also cautioned against overconfidence, saying it is too soon to suggests that the war is at a turning point.
Gates said that the situation in Afghanistan remains serious, but it has stopped deteriorating.
The top U.S. commander in Afghanistan, General Stanley McChrystal, said the next goal is to retake Kandahar, the Taliban's traditional stronghold.
McChrystal said that, unlike Marjah, the operation to secure Kandahar will be more gradual as more U.S. troops arrive in the region. He declined to give a timetable for the offensive.
Gates also warned Iran about offering help to the Taliban. He accused Tehran of playing a "double game" in Afghanistan -- being friendly to the Afghan government while at the same time trying to undermine the U.S.
Pentagon press secretary Geoff Morrell later said Gates was referring only to actions the U.S. might take inside Afghanistan and not to a wider confrontation with Iran.
Also Monday, Afghan police backed by U.S. troops killed two would-be suicide bombers in eastern Khost province bordering Pakistan.
Police say the gunmen set off a bomb and then fled to a building next to a police station, where they were surrounded and killed in a shootout.