Kyrgyzstan is becoming a key US partner in the war in Afghanistan because conventional supply routes through Pakistan are closed, the defense secretary said. Kyrgyzstan is the site of a transit center for the US military at the Manas Air Base that serves as a major stopping point for military supplies en route to Afghanistan. US Defense Secretary Leon Panetta said during his first official visit to Kyrgyzstan that the Manas was critical to the US  mission in Afghanistan. \"(It\'s been) extremely important in recent months, since our (ground transit routes) have closed in Pakistan,\" he was quoted by the Pentagon as saying. Kyrgyz President Almazbek Atambayev told Radio Free Europe/Radio Liberty last year he would rather see Manas used as a civilian airport. He expressed concern that his country would be caught in the crossfire of any broader US military engagement with any nearby countries like Iran. The Pentagon said it pays about $60 million per year to use the base. Defense Department officials said that arrangement holds through 2014 when international forces are expected to leave Afghanistan. Kyrgyzstan is the only country to have both Russian and US  military installations.