SHARM EL-SHEIKH, Egypt (Reuters) - The United States will have to negotiate with Syrian President Bashar al-Assad for a political transition in Syria and is exploring ways to pressure him into agreeing to talks, U.S. Secretary of State John Kerry told CBS News in an interview. Washington has long insisted that Assad must be replaced through a negotiated, political transition, but the rise of a common enemy, hardline militant group Islamic State, appears to have slightly softened the West's stance towards him. In the interview broadcast on Sunday, Kerry did not repeat the standard U.S. line that Assad had lost...