Washington: Moody's has cut its credit rating for Greece to a deep-junk "Caa3", warning it is now less likely that official creditors will support the country, whatever happens in Sunday's referendum.

The one-notch cut took Greece's rating to just two steps above "default", and came after both the expiration of the country's European Union bailout program without a replacement on Tuesday, and Athens's default on its debt to the International Monetary Fund.