The U.S. and other powers are investigating suspected efforts by Libyan militia leader Khalifa Haftar to raise funds through oil deals, including with Emirati brokers and Venezuela, according to U.S., European and Libyan officials. The United Nations and the official Libyan government are probing a Dubai-based ship charterer for possibly helping Mr. Haftar to market fuel in the Mediterranean, the officials said. The U.S. has also begun scrutinizing a trip Mr. Haftar may have made to Caracas in what some officials say was an…