The University of California, Berkeley has begun cutting down trees at the center of a dispute over its plans to clear the area to make way for a new sports center.

Protesters sitting in a nearby oak on Friday refused to move.

University spokesman Dan Mogulof says school officials want to make it difficult for the tree protesters to remain, although they do not want anyone to get hurt or to get into a confrontation.

Campus officials are calling on the protesters to come down peacefully.

The California Court of Appeal on Thursday denied a request from two citizens groups for an injunction barring construction of the athletic training facility. The groups say they plan to take the case to the state Supreme Court.