WASHINGTON - The International Monetary Fund's new chief foresees "real nasty consequences" for the U.S. and global economies if the U.S. fails to raise its borrowing limit. Christine Lagarde, the first woman to head the global lending institution, said in an interview broadcast Sunday that it would cause interest rates to rise and stock markets to fall. That would threaten an important IMF goal, which is preserving stability in the world economy, she said.