SAN FRANCISCO — Internet icons Google Inc. and Yahoo Inc. are intensifying their efforts to become more accessible on mobile phones, a platform widely seen as the next big battleground for the longtime rivals.

The Silicon Valley foes underscored their commitments to the mobile market yesterday at the International Consumer Electronics Show in Las Vegas, where they brandished dueling partnerships.

As more people spend more time using their mobile phones for things besides talking, Google and Yahoo believe they can boost their profits by selling advertising targeted at consumers outside their homes and offices. Spending on mobile ads is expected to rise to about $1.5 billion this year and at least double in size by 2010.

Sunnyvale-based Yahoo is hoping to fare better in mobile search than it has in traditional Web search, where Mountain View-based Google has been steadily increasing its already sizable lead to devour an even larger chunk of online ad spending.

The lopsided competition has punished Yahoo's stock, which has plummeted by about 35 percent over the past year. The downturn triggered a reorganization that will include the March departure of Yahoo's chief operating officer, Dan Rosensweig.

Both Google and Yahoo will feature some of their products on mobile phones manufactured by Samsung Electronics under deals announced at the nation's largest gadget-fest.

Yahoo also hammered out similar arrangements with several other leading handset makers, including Motorola Inc., Nokia Corp. and Research In Motion Ltd., as it tries to popularize a new feature designed to make it easier for consumers to find information while they are on the go.

With its "oneSearch" product, Yahoo believes it will do a better job delivering vital information to mobile phone users without forcing them to click through as many links as conventional searches on the Web require.

OneSearch is a part of a major upgrade of mobile software Yahoo unveiled at last year's electronics show. The company plans to aggressively promote the software on its Web site, where visitors will be able to determine if the applications are compatible with their phones. Yahoo says the software currently works on about 70 different phone models.

With its Samsung alliance, Google also is hoping to make it simpler to use its search engine, maps and e-mail on mobile phones.

Mobile search has been slow to take off, largely because handset providers have different operating standards that have made it difficult to develop applications for a mass market. The small screens and keyboards of mobile handsets also make searching more cumbersome.