WASHINGTON (AFP) — The United States is entangled in an Islamist web from Afghanistan to India that exposes its reliance on Pakistan as a central but increasingly fragile ally in the war on terror, analysts say. The 60-hour siege last month in Mumbai, even if it is eventually proven to have been masterminded by Kashmiri separatists, advances broader Islamist aims in Afghanistan, Pakistan, India and beyond, they add. And nuclear-armed Pakistan, which has long backed various Islamist groups, is more than ever central to the growth of the militant problem in all three countries and a key to their solution....