See also: Apple iPhone review
Bank of America analyst Scott Craig also predicted in the report that up to eight million of the devices will have been produced by the third quarter of the year.
"Our latest channel checks point to a significant production build of a 3G iPhone beginning in the month of June after an initial small build in May," Craig told news agency Reuters.
Both Apple and AT&T, the official service provider for iPhone in the US, refused to comment. Last year, AT&T predicted that it would be able to sell a 3G version of iPhone in 2008.
A number of analysts expect Apple to launch an advanced iPhone to coincide with its developer conference in June.