WASHINGTON (Reuters) - The United States will repel any attempt to take Syria’s oil fields away from U.S.-backed Syrian militia with “overwhelming force,” whether the opponent is Islamic State or even forces backed by Russia or Syria, the Pentagon said on Monday. The U.S. military announced last week it was reinforcing its position in Syria with additional assets, including mechanized forces, to prevent oilfields from being taken over by remnants of the Islamic State militant group or others. U.S. Defense Secretary Mark Esper offered some of his most detailed remarks to date about the mission at a news briefing on...