Statistics issued Monday by Net Applications seem to run counter to recent reports suggesting that Google’s (GOOG) Android is rapidly overtaking Apple’s (AAPL) iPhone OS, starting in the U.S.

The results are summarized in the pie chart at right, which is labeled “Total Market Share,” but which actually represents share of visits to the websites of Net Applications’ clients — a total of 160 million visitors a month.

According to the metrics firm’s brief report, the iPhone not only maintains a large lead over Android, but it actually gained more global share in May, going from 30.3% to 32.8% while Android went from 5.3% to 6.2%.

In terms of its percentage increase, however, Android is growing faster. Its share grew nearly 17% month over month, while the iPhone’s grew only 8.25%, albeit from a much larger base.

Java ME (for micro-edition), which is used by many older smartphones, still maintains the No. 1 spot as the most popular platform for mobile browsing. But according to Net Applications, it is rapidly losing share to Android and the iPhone.

[Follow Philip Elmer-DeWitt on Twitter @philiped]