TAIPEI, Dec 17 (Reuters) - Taiwan will maintain stability in its foreign exchange rate, a central bank official told Reuters on Thursday, after the U.S. Treasury put the island on its currency monitoring list. The official made the comment on condition of anonymity. Taiwan was last formally labelled a currency manipulator by the United States in December 1992, but was later put on the U.S. Treasury monitoring list in 2016 and 2017. (Reporting by Liang-sa Loh; Writing by Ben Blanchard; Editing by Tom Hogue)