Boulder, Colo. ? Trying to shed its image as one of the biggest party schools in America, the University of Colorado is demanding that its fraternities put off the traditional fall recruiting period known as rush until the spring semester.

The 16 fraternities at Colorado have said they are eager to help the school curb problem drinking, but they have balked at postponing rush, complaining it will cost them enrollment dues and wreck recruiting.

“We can’t afford to defer rush. It will kill off the greek system in terms of numbers. Whether that’s the university’s intent, we’re unsure,” said Ryan Lynch, a member of Sigma Nu and the internal vice president of the Interfraternity Council.

The school — which has 24,700 undergraduates, about 10 percent of whom are in fraternities or sororities — contends freshmen need time to adjust to college before pledging a fraternity.

The university is threatening to deny fraternities the use of such things as campus meeting rooms, playing fields and lists of incoming freshmen unless they comply. Sororities at Colorado have agreed to defer their rush period until spring, university officials said.

At Kansas University, fraternities have rush during the summer and sororities when classes begin in the fall.

Colorado’s reputation has been tarnished by a scandal in which investigators said alcohol, drugs and sex were used to entice football recruits to campus, and two years ago it was dubbed the No. 1 party school by the annual Princeton Review.