The device was shown as part of the presentation on Android, the new operating system for the mobile platform.
Reports that the phone bore identifying marks were denied by Google, which has refused to confirm that the exercise was a demonstration of the product before release.
The handset is believed to be manufactured by HTC and provisionally called “Dream”.
The suspected release date for Dream is late October, and the formal announcement of the mobile is expected to be held by Google and T-Mobile next week in New York, with HTC hoping to ship 600,000 to 700, 000 units this year across the globe.
The handset, which features a slide-out keyboard, an inbuilt accelerometer and Global Positioning System, is expected to compete against Apple’s iPhone in the run-up to Christmas.