June 23 (Bloomberg) -- Google Inc., owner of the world's most popular search engine, said it's on schedule to deliver the first mobile phones that run its Android operating system to customers by the second half of this year.

Momentum for the project is building from carriers, handset makers, developers and consumers, Mountain View, California-based Google said today in an e-mailed statement.

Google is developing Android -- which will let users check e-mail, search the Web and watch videos on their phones -- to compete with systems offered by Microsoft Corp., Apple Inc. and Research In Motion Ltd. Online advertising on phones in the U.S. may jump to $4.8 billion by 2011 from $1.6 billion this year, according to New York-based research firm EMarketer Inc.

``They look at mobile as one of the emerging, multi-decade opportunities,'' Scott Kessler, an analyst with Standard & Poor's in New York, said in a Bloomberg Television interview. ``This is about market share for Google right now.''

Google fell $1.22 to $545.21 at 4 p.m. New York time in Nasdaq Stock Market trading. The stock has dropped 21 percent this year.

The Wall Street Journal reported today that Android is experiencing delays as wireless carriers such as T-Mobile USA Inc. and Sprint Nextel Corp. struggle to implement the technology. Android-based phones might not make it onto the market until the end of 2008 or sometime next year, the Journal said, citing people familiar with the matter.

Growing Market

Google is seeking the same payoff from mobile-phone advertising that it reaped in the computer-based online ad market, which analysts at Piper Jaffray Cos. value at $41 billion worldwide last year.

Google is going up against companies such as Nokia Oyj, the world's largest maker of mobile phones, and Research In Motion, which together accounted for 58.6 percent of the market for advanced handsets in the first quarter, according to research firm Gartner Inc. Apple's iPhone was third with 5.3 percent.

Shipments of so-called smart phones, which have Internet browsing and e-mail access, increased 29 percent to 32.3 million units. North America led that growth, where shipments more than doubled from a year earlier, Stamford, Connecticut-based Gartner said.

There are more than 3.3 billion mobile phones worldwide, about one for every two people on the planet. By 2010, that number is expected to jump to 4 billion, or triple the number of personal computers, Gartner said.

Google offered the Android platform to service providers, chip makers and mobile-phone sellers in November, forming the Open Handset Alliance, which has more than 30 members. Among them are Motorola Inc. and speech-recognition software maker Nuance Communications Inc.

Unlike other software makers such as Microsoft, Google is giving the operating system to developers free of charge.

To contact the reporter on this story: Amy Thomson in New York at athomson6@bloomberg.net

Last Updated: June 23, 2008 17:02 EDT