MANILA, Jan 5 (Reuters) - The Philippines' central bank said on Friday it is necessary to keep monetary policy settings sufficiently tight until a sustained downtrend in inflation becomes evident.

It will take appropriate action as needed to bring inflation back to target, Bangko Sentral ng Pilipinas said in a statement after the statistics agency reported that inflation was at 3.9% in December. (Reporting by Neil Jerome Morales and Mikhail Flores; Editing by Kanupriya Kapoor)