New York City's mayor is facing off with Yale University over efforts by the NYPD to monitor Muslim student groups.

The Associated Press revealed Saturday that NYPD officers had kept close watch on websites and blogs maintained by Muslim student associations across the northeast U.S., and in one case sent an undercover officer on a rafting trip with students from the City College of New York.

Yale President Richard Levin said in a statement Monday that monitoring of students based on religion was "antithetical" to the schools' values.

New York Mayor Michael Bloomberg defended the practice. He says there is nothing wrong with officers keeping an eye on websites that are available to the general public.

He says, "I don't know why keeping the country safe is antithetical to the values of Yale."

(Copyright 2012 by The Associated Press.  All Rights Reserved.)