Enlarging faucet hole in concrete countertop

Hi all, I recently replaced my kitchen faucet. All went well except that the new soap pump doesn't quite fit into the old pump hole. I need to enlarge the existing 1" diameter hole to 1 1/8". Only the top 1/4" needs to be enlarged and I could make it up to 1 1/2" diameter if I had to. I don't think I'll need to, but there is some room for the enlargement to not be a perfect circle. The countertop is concrete with small quartz aggregate. I'm guessing I'll want to use some sort of diamond tool, but I'm not sure if this would be a drill bit (step bit?) or some sort of grinding wheel for a dremel or angle grinder. Any thoughts? Thanks, Jeff