KABUL (updated)--More NATO troops will die in Afghanistan as violence mounts over the summer, but Washington's goal of turning the tide against the insurgency by year's end is within reach, the top US military officer said on Sunday. The remarks by Chairman of the Joint Chiefs of Staff, Admiral Mike Mullen, on a visit to the country, came as the Taliban said they were holding captive one of two US servicemen who strayed into insurgent territory, and that the other had been killed. It also comes less than a week since a major international conference in Kabul agreed that the Afghan government should aim to take responsibility for security in all parts of the country by 2014. Mullen, who called the troops' disappearance an "unusual circumstance", said there would be more violent incidents to come, but the US military was doing everything possible to find the missing men. A spokesman for the NATO-led force declined to comment on the Taliban's announcement it was holding one of the men. The Afghan government said on Sunday it was checking reports from villagers that civilians had been killed in a raid by foreign forces in Sangin, in southern Helmand province, on Friday. The NATO-led force said it was aware of reports of the incident and was investigating, but would not comment further until further details were available. Such incidents have triggered outrage in the past among the population against the international troops whose mission is to protect them. Elsewhere, Taliban guerrillas captured a remote district from the Afghan government after days of clashes in eastern Nuristan province, officials said on Sunday. A spokesman for the Interior Ministry said police were working to recapture Barg-i-Matal, a district that has changed hands several times in recent months. U.S. troops pulled out of the remote and mountainous region in line with Washington's strategy of giving priority to protecting population centres. Violence in Afghanistan is at its highest of the nine-year war as thousands of extra U.S. troops, dispatched by President Barack Obama in December, step up their campaign to drive insurgents out of their traditional heartland in the south. Last month was the deadliest for foreign troops since 2001, with more than 100 killed, and civilian deaths have also risen as ordinary Afghans are increasingly caught in the crossfire. "As we continue our force levels and our operations over the summer ... we will likely see further tough casualties and levels of violence," Mullen told a news conference in Kabul. Despite the rise in casualties, Mullen said "slow but steady" progress was being made and that Washington's strategy of reversing the insurgency's momentum was still obtainable by the end of the year. The next months would be crucial, he added. "No one is declaring victory but there is progress," said Mullen. "I believe that goal is still achievable and certainly the proof of that will be what happens over these next many months in what is a very challenging period."
