Last month Apple announced that the white iPhone 4 had "proven more challenging to manufacture than expected", which meant sales would be delayed until the end of July.
Yesterday the company said the white models "have continued to be more challenging to manufacture than we originally expected" and now won't be available until later this year.
Apple recently revealed it had sold over 3 million units of the new (black) iPhone in the first three weeks since launching the phone on 24th June.