Playing DVD's in HD-DVD at higher resolution?

Is it possible to take a movie file that is high def and burn it on a DVD and play it on a HD-DVD player?

Does a DVD force the movie to be 480? Or can 720 content be burned on a DVD and then played on a HD-DVD player?

I am not asking about playing a 480 DVD and upconverting to 720. I am asking about burning 720 on a DVD and playing it without losing quality.