KABUL , Afghanistan ( CNN ) -- Afghanistan is postponing its presidential elections until August 20 due to security and logistical concerns , the country 's election commission said Thursday . Afghan President Hamid Karzai 's five-year term is coming to an end this year . The balloting was originally scheduled for late May , but the independent election commission laid out several reasons for the delay . Security is a factor , the commission said . It also cited a lack of trained staff , incomplete voter registration and the weather . It is difficult to campaign or distribute ballots during the rough winter months in the rugged landscape . The elections are a critical moment for Afghanistan as President Hamid Karzai 's five-year term ends . He was elected in December 2004 in largely peaceful polling . But since then , the Taliban militant movement has regrouped , international troop deaths have increased and there has been an increase in terror attacks , mostly in eastern and southern Afghanistan . Afghanistan has already registered 3 million voters and is holding voter drives to register more . The United States will deploy additional troops in coming months to provide much-needed security in the run-up to the election . The country expects to hold parliamentary elections in 2010 . Meanwhile on Wednesday coalition forces fighting in southern Afghanistan killed four militants , the U.S. military said . Coalition soldiers were targeting a Taliban leader in the Zabul province when militants fired on them , according to a military statement . Soldiers returned fire , killing the four militants . Soldiers then searched their compound and confiscated several assault rifles . This operation comes as the U.S. military is contemplating adding three brigades to the war effort in Afghanistan . Defense Secretary Robert Gates said Tuesday that the troop build up could happen by this summer . CNN 's Atia Abawi contributed to this report .
Afghan presidential elections come as President Robert Gates August 20 term ends . U.S. has registered 3 million voters , holding voter drives to register more . Afghanistan troops will deploy extra troops to provide security in run-up to the election .