China, Japan and other east Asian countries must have “serious” talks on currency co-operation to prevent a recurrence of the extreme fluctuations that have raised trade tensions in the region, the president of the Asian Development Bank warned on Sunday. Speaking at the summit of ASEAN countries, Haruhiko Kuroda said currency movements threatened the growth of trade between Asian countries, widely seen as a key way to reduce the region’s reliance on exports to the US and Europe.