S&P says its A/A-1 sovereign credit ratings on Israel remains unchanged.
The Israeli Finance Ministry said it was not aware of the downgrade and had no immediate comment.
The U.S. has guaranteed $19 billion in Israel-issued bonds since the 1990s, giving Israel favorable terms of interest when borrowing.
Israel has not tapped the entire pool.
Copyright 2011 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.