Remove welcome screen from Live USB?

I created a Live Ubuntu 10.10 with persistent storage on a USB drive. On every boot the Welcome screen appears where you can select the language and choose to try Ubuntu Live or to install Ubuntu.

I'd like to remove this screen and have Ubuntu directly start into Live mode with a specific language. How could I achieve that?

You should be able to prepare a LiveUSB image for yourself with the Ubuntu Customization Kit
(reference screenshots).
But, I think you should consider installing from a LiveCD to your USB rather than burning the image to your USB.

I would like to comment, since this is one of the first results on google, that you should NEVER install Ubuntu on a flash medium as a regular installation. Live usb's make a lot of changes to the way Ubuntu loads in order to prevent damage to your pendrive. There are things you can do to an installation of ubuntu in order to prevent this damage, but do not ever just simply install Ubuntu onto a pendrive unless you do not care if it becomes damaged.

You can install Ubuntu directly to a flash medium if you disable the use of swap and switch it to load the /tmp directory directly to the RAM instead of using a /tmp folder on your device. This is extremely important because flash has a limited number of rewrites, and using it for any sort of temporary memory will cause it to become unusable exponentially quicker. LiveUSB starts up with a static image of Ubuntu, with all modifications (the Persistence portion of the usb) loaded from the casper-rw file (or partition if you deleted the file and created a partition on your flash drive labeled casper-rw). this prevents the use of the flash drive for any sort of temporary storage and prolongs the life of the device.

Those of you who have read this page and simply installed ubuntu to the flash drive without disabling swap/moving the /tmp folder to store data in ram, should do that now in order to prevent damage to your flash drives.

If you want anything more than a live-usb version of Ubuntu on your flash drive, you really should just install it to a hard disk (portable or internal, just a device that is not simply a flash medium) in order to proficiently use it/prevent hardware damage.