“Running a Web site and a search engine is one thing,” said Mr. Weide of IDC. “But developing a phone is a whole different game. It will not be easy for them.”

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Mr. Weide added that Google’s impact on the industry will depend to a large extent on its ability to sign deals with wireless carriers that distribute hundreds of millions of phones each year and often control what software and services run on them.

Some carriers, especially in the United States, are likely to give Google a cool reception. Companies like Verizon Wireless and AT&T have spent billions of dollars building and upgrading their networks, establishing relationships with customers, subsidizing handsets and creating their own mobile Internet portals. Now they want to make sure those investments pay off, in part, through mobile advertising, and they see Google and other search engines, who are after the same ad dollars, as competitors.

As a result, most carriers in the United States have chosen to shun the major search engines for now. Instead, they have promoted the search engines and ad systems of small technology companies like JumpTap and Medio Systems, whose services they can stamp with their own brands.

Most carriers declined to comment on Google’s plans. But Arun Sarin, the chief executive of Britain’s Vodafone Group, which offers the Google service on its phones, said it was not clear what compelling functions Google would offer that are not already available.

“What is it that is missing in life that they are going to fulfill?” Mr. Sarin said. “It is not a no-brainer. You can reach Google already through a number of devices. You don’t need a Google phone to do that.”

Google’s desire to loosen the carriers’ control over their networks has hardly been a secret. The company recently lobbied the Federal Communications Commission to impose rules on any carrier who wins a coming auction for valuable wireless spectrum. The rules, which the F.C.C. adopted despite opposition from Verizon and others, require that the network using a portion of that spectrum be open to any handset and software applications from any company.