VIENNA, Dec 11 (Reuters) - The head of the U.N. atomic agency asked member states on Thursday for 4.6 million euros ($5.7 million) in extra funding "as soon as possible" to help pay for its monitoring of an extended nuclear deal between Iran and six world powers. Iran and the United States, France, Germany, Britain, China and Russia failed last month to meet a self-imposed deadline to end a 12-year dispute over Tehran's nuclear programme, giving themselves seven more months for diplomacy. As a result, an interim deal reached last year will remain in force. ...