LONDON, July 22 -- The world refined tin market was in a surplus of 6,600 metric tons in January to May, the World Bureau of Metal Statistics said Wednesday.

This is up from a surplus of 5,700 tons during the same period a year ago, the WBMS said.

The surplus was largely due to exceptionally weak U.S. imports in January, April and May.

World refined tin output rose 17,900 tons during the period to 145,200 tons, although output in January to May in 2009 had been unusually low because of shutdowns by Chinese smelters.

World refined tin demand rose 14% on the year to 138,600 tons.