Apple CEO Steve Jobs speaks introduces the Apple iPhone 4 in Cupertino, California on July 16. Apple said it is postponing the launch of a white version of its new iPhone 4 smartphone to later this year, due to manufacturing problems, leaving customers with only a black option.

Apple said Friday it is postponing the launch of a white version of its new iPhone 4 smartphone to later this year, due to manufacturing problems, leaving customers with only a black option.

It was the second time Apple has announced a delay in the white version of the hot-selling 4.

The Cupertino, California-based gadget maker said just before the June 24 launch of the next-generation smartphone that the white version would not be on the market before July because of manufacturing problems that it has yet to explain.

"White models of Apple's new iPhone 4 have continued to be more challenging to manufacture than we originally expected, and as a result they will not be available until later this year," Apple said in a brief statement on Friday.'

The company added that the availability of the "more popular" iPhone 4 black models is "not affected."

Apple says the is its most successful product launch, with more than three million sold in the first three weeks after its debut.

But the smartphone, the fourth generation of a multifunction phone that has revolutionized the sector, suffers from reception problems linked to its new design.

A week ago, Apple chief executive Steve Jobs interrupted his vacation to announce at a news conference that Apple would offer free rubber cases to protect the metal border where the antenna is located.

says demand for the new iPhone 4s has outstripped production capacity, leaving numerous markets with back orders.

According to specialist websites, Apple's white-model problem is the difficulty in developing a white paint formula for the case that is opaque enough to produce an appealing white and transparent enough to allow signal transmissions.