Google on Tuesday officially unveiled its own smart phone, which represents the Internet search giant's strongest challenge against Apple's popular iPhone.

Dubbed Nexus One, the new handset is an exemplar of what's possible with mobile phones on Google's Android operating system, Google executives said at a press conference held at the company's headquarters in Mountain View, the U.S. state of California.

Mario Queiroz, Google's vice president of product management, said Nexus One belongs in the emerging class of devices which the company calls "super phones."

Manufactured by HTC Corp., Nexus One features a 3.7-inch OLED display, a 5-megapixel camera and delivers speed up to 1 GHz.

The handset runs on Android 2.1, the latest version of Google's mobile operating system that includes innovations such as a voice-enabled keyboard.

Google noted that Nexus One is the first phone to be sold directly to consumers through its new web store, touted by the company as a new model for consumers to buy a mobile phone.

Through the web store hosted by Google, consumers can buy NexusOne without service or purchase the phone with service from one of Google's operator partners.

Nexus One is initially available from the Google web store in the United States without service for 529 U.S. dollars or starting at 179 dollars with a two-year contract from T-Mobile USA, Google said.

It added that Verizon Wireless in the United States and Vodafone in Europe plan to offer services to customers in their respective geographies in the near future.

"In the coming months Google plans on partnering with additional operators, offering consumers access to a broad set of service plans. In the future we expect to launch more phones with Android handset partners and to expand the web store to more countries," the company said in a statement.