By Leika Kihara WASHINGTON (Reuters) -The Bank of Japan must keep monetary policy loose and move very gradually in raising interest rates as global trade uncertainty clouds the economic outlook, a senior International Monetary Fund official said on Wednesday. Japan's economy has performed better than expected so far this year on robust consumption and exports, with Tokyo's trade deal with Washington easing some uncertainty, said Nada Choueiri, deputy director of the IMF's Asia and Pacific Department. Bu ...