Likely could not "relocate" them if and once the nest is established -- parents would probably abandon a disturbed nest, however,

Since they're rebuilding rather than sitting on eggs in the nest yet, see that don't get established. Use this opportunity to force them elsewhere by knocking down their efforts daily -- they'll eventually get the message.

You could put up something that will discourage them such as a piece of window screening that you could move later and/or something with motion and/or noise to cause them disquiet -- such as adding a wind chime or wind sock -- anything to disturb them enough to seek a safer place elsewhere to nest.

Check with the nearest Audubon Society chapter. I'm sure they can advise you.