The International Monetary Fund (IMF) warned today, Thursday, that a default on U.S. debts resulting from failing to raise its debt ceiling would have "extremely serious consequences" for both the U.S. and global economies. IMF spokeswoman Julie Kozak stated, "U.S. authorities need to be cautious about new vulnerabilities in the U.S. banking sector, including regional banks, which may arise... amid the significant rise in interest rates."