In Shulchan Aruch, Orach Chaim, Siman 128 Sif 22, the Mechaber writes that, regarding Birkas Kohanim, "we attempt to have the caller [i.e. the one who says the words of the Bracha before the Kohanim] be an Israelite". This contrasts what was said a bit earlier regarding how the process works if the Kohein is the Chazzan.
However, does anyone comment on whether the "caller" could be a Levi? The words of the Mechaber say "Israelite", but was that used simply to mean a non-Kohain, or is an Israelite preferred?