By Warren Strobel and Mariam Karouny GENEVA/BEIRUT (Reuters) - Russia and the United States put aside bitter differences over Syria to strike a deal on Saturday that by removing President Bashar al-Assad's chemical arsenal may avert U.S. military action against him. After three days of talks in Geneva, U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov demanded Assad account for his secret stockpile within a week and let international inspectors eliminate all the weapons by the middle of next year - an "ambitious" target, Kerry said. ...