Google's first mobile phone is set to launch on T-mobile in the U.S. later today (it all kicks off at 16:30 CET), but it seems like most of the details about the G1 handset have already leaked online and although the handset design might not appeal to everyone, the specifications are at least up there with the latest devices.

We're not sure we trust all of the information and some details are still a bit sketchy, but the G1 will feature a 480x320 HVGA screen, it will have a built in GPS, but it will only have basic Bluetooth audio support for headsets as stereo audio is not supported. It will also feature a 3.1Megapixel camera, but supposedly you can't use it for shooting video.

The G1 will also support up to 8GB memory cards, we presume microSD, but no format was mentioned. The battery is meant to be good for up to five hours talk time and 130h standby. 3G support is, of course, part of the package, but there seems to be some restrictions on who can buy the G1 in the U.S., as T-mobile won't sell it in areas that don't have 3G support.

You'll also have to sign up for a data package and you need to have a Gmail account to be able to use some services. Pre-installed "one-click" applications include Google Maps, Gmail, YouTube (shouldn't the G1 really have video recording support?), Calendar and Google Talk.

The handset should measure 117x55x16mm (HxWxD) and the weight should be 159g, which seems a bit heavy. It looks a lot better in black compared to the white color we've seen in the past, but we're still not keen on the odd slide design.

We should know the full details in a few hours, but we're hoping there will be more good news than bad news, as at the moment we're not overly enthusiastic about the G1; and here's fingers crossed that Europe gets a better Android device than the U.S.

You can find some more details and some new pictures here.