Tokyo, Aug 6 (BridgeNews) - Japan had a 179.653-billion-yen trade surplus on a custom-cleared basis in the first 20 days of July, down 67.2% on the year, the Ministry of Finance announced. The data confirm weakness in overseas demand and indicate the trade surplus for July 1-31, to be released in mid-August, may show a fall on the year, resulting in declines for 13th straight months.