Mobile phones designed around Google's Android software may not be available until the fourth quarter of this year, and some companies are struggling to even meet that deadline, the Wall Street Journal reported Sunday, citing unidentified sources.

When Google and 30 partners announced Android last November, the Internet search giant said new phones would be on the market by the second half of this year.

But the Journal reports that some mobile network operators, such as Sprint Nextel, have abandoned the idea of launching an Android-based handset this year due to delays. Other operators, such as China Mobile, have delayed their planned roll-out of Android-based handsets to later this year or early next year, the Journal said.

The handsets aren't the only problem. Software developers are also grumbling about Android, the Journal said. Google continues to make changes to the software, making it difficult for other software developers to create programs that work with Android.

Wireless carriers have found customizing Android to promote their Internet services a problem, and some handset makers are taking longer than expected to integrate the software, test it and build custom user interfaces to meet the specifications of mobile phone carriers, the Journal said.

Taiwan's High Tech Computer is one company that has already said it is developing an Android-based handset. The company says it expects the mobile phone to be out in the fourth quarter.

Samsung Electronics is also reportedly working on an Android handset.