T-Mobile USA is set to launch the first cell phone to run Android, Google's free software platform, later today.
The launch of the G1 will take place in New York about 16h30 our time.
Android was widely hailed at the response to Apple's iPhone when it was first offered to cell phone developers last year.
It is estimated that T-Mobile would probably sell about 400 000 of its phones in the US market this year, giving Google just 4% of the smart phone market.
It is expected that the G1 will be based on a design by HTC. It will probably have a touch screen and a slide-out full-alphabet keyboard.
The phone will carry the Google brand.