The International Skating Union is warning member nations that involvement with a rival splinter group could get them suspended.

In a letter to members Monday, figure skating's governing body said support for the World Skating Federation is ''absolutely incompatible'' with the ISU.

''It is evident from their documents and declarations that the group is hostile to the ISU. It has attacked the union and its president. It is, in fact, a declared competitor of the ISU and aspires to act in a way which could destroy the ISU,'' according to the letter from the ISU council, obtained by The Associated Press.

Backed by some of the sport's biggest names, the World Skating Federation announced its formation last Tuesday with the goal of replacing the ISU as the sport's governing body. The WSF claims the sport has lost credibility and integrity under current ISU leaders, particularly with the use of an anonymous, interim scoring system this season.

In its letter, the ISU said support for the WSF would violate the ISU's constitution. According to the constitution, ''members shall not participate in any activities, national or international, against the integrity, the exclusive role and interests of the ISU.''

Judges or referees who violate the constitution would no longer be allowed to participate in ISU events. A national federation could be suspended, possibly costing that country the right to enter skaters in the Olympic Games or world championships.

''We can't ask anyone to join, obviously, because it could jeopardize the member and potentially their athletes, and we will never ask a member to put their athletes in jeopardy,'' said Ron Pfenning, acting president of the WSF. ''The task we have before us is to get the majority of members to endorse our principles.''

But even getting federations go that far could be difficult.

The U.S. Figure Skating Association's executive committee voted 8-0 last Tuesday to endorse the WSF's principles, including ''athlete and coach representation, geographic representation, transparency, ethics, accountability, integrity, and zero tolerance.''

The executive committee also unanimously approved a resolution stating that it could not endorse the group itself because it had ''neither the time nor the opportunity to be fully informed'' about the WSF.

After WSF co-founder Jon Jackson announced the USFSA's endorsement of the splinter group's principles, the USFSA issued a release distancing itself. Citing its resolution not to support the group, the USFSA said ''it would be inaccurate and untrue for anyone to suggest that the USFSA leadership has endorsed the proposed new entity.''

''We were just making it clear what we were doing,'' said Phyllis Howard, president of the USFSA. ''Endorsing the principles, those are universal principles. We needed to make it clear we were not endorsing the entity itself.''

But Jackson said the USFSA's release and the ensuing confusion hurt the WSF's credibility, and that he would call for Howard to resign.