Yahoo Inc has struck a deal to expand the role of its services on cellphones of the world's second-largest handset maker Samsung, as the two battle larger rivals on the wireless market.

The role of mobile services and software has increased sharply since Apple and Google entered the industry, forcing traditional phone makers like Samsung and Nokia to hurry to build up their offerings.

Weak services and software offerings are seen as a potential stumbling block for the ambitious plans of Samsung and its domestic peer LG Electronics in their plan to win a bigger share of the smartphone market.

Samsung and Yahoo, who have partnered since 2007, said the expansion of their contract will give millions more Samsung phone owners easy access to Yahoo's services, starting from May.

The new contract includes phones running Samsung's own Bada platform and Google's Android platform, which will have better access to a wide range of Yahoo services including mail, messenger, search, news and calendar. (Reporting by Tarmo Virki; Editing by Jon Loades-Carter)