Key issues may persist in Iran-UN nuclear talks - diplomats

* Iran and U.N. nuclear watchdog to meet again on Jan. 16 * Both sides reported progress in last week's talks * Diplomats in Vienna say notable differences remain * World powers closely watch Iran-IAEA negotiations VIENNA, Dec 19 (Reuters) - The United Nations nuclearwatchdog and Iran may have made headway in talks on Tehran'sdisputed atomic activities but important points remain to besettled ...