Microsoft said on Monday it had signed a deal with LG Electronics, under which the world's third-largest cellphone maker will use Windows software in most of its smartphones.

A majority of their smartphones will use Windows, Andy Lees, the head of Windows' wireless unit, told Reuters in an interview.

Small handset vendor HTC is currently the world's largest maker of phones using Windows software.

While Samsung Electronics, Motorola and Sony Ericsson have Windows phones on the market, they make up only a small proportion of their offerings. Microsoft also joined a growing number of companies in the industry launching or revamping online stores for consumers to download and install software directly to their phones for services such as finding directions or playing games.

The company also rebranded its wireless offering to Windows from Windows Mobile, and launched a backup service for data -- like contacts and pictures -- stored on Windows phones.

Microsoft, whose Windows mobile operating system used to be the second-most popular for smartphones after Nokia's Symbian, has been overtaken by Apple and BlackBerry maker Research in Motion.

(Reporting by Tarmo Virki; Editing by Erica Billingham)