WASHINGTON (Reuters) - The top US military official flew to Germany for an unannounced meeting on Friday with his commander in Afghanistan to discuss a request for more troops, military officials said. Admiral Mike Mullen, chairman of the Joint Chiefs of Staff, met for several hours at a US military base in Ramstein, Germany, with Gen. Stanley McChrystal, who is expected to hand over his troop request in the coming hours to US Defense Secretary Robert Gates. President Barack Obama, who has described himself as a skeptical audience when it comes to sending more troops, is not expected to examine McChrystals request until he completes a broad review of his 6-month-old counterinsurgency strategy, Pentagon officials have said. McChrystal has said the Afghan mission was likely to fail without additional troops but such a request could be a hard sell given souring public opinion and a rising death toll in the 8-year-old conflict.