Problems within the Muslim-Croat federation over who controls what in Sarajevo - even the color of its police uniforms - suggest the Bosnian peace pact could be unraveling.

Looting, violence and burning continued Thursday in the suburb of Ilidza and the central Grbavica district, which the Serbs must hand over to the federation Tuesday.A NATO spokesman Thursday took the unusual step of publicly warning both sides to salvage the federation, brokered by the United States in spring 1994 to end a year of fighting between Muslims and Croats.

"The success of the peace agreement depends entirely on the cohesion of the federation," said Maj. Simon Haselock. "At the moment, the parties appear to be making few substantive efforts to make it work."

"The federation is in free fall," said an international official in charge of implementing the Bosnian peace accord who insisted on anonymity. "It is up for grabs now."

The Muslim-Croat federation has never gained full acceptance on either side. Yet it is the cornerstone of the U.S.-brokered peace accord. If it falls apart, international officials concede, the Bosnian Serb republic that controls half of Bosnia will feel no obligation to abide by that agreement.

Croatian Prime Minister Zlatko Matesa and Foreign Minister Mate Granic came to Sarajevo Thursday after Bosnian police for a second day turned away nine Bosnian Croat counterparts who were to share the policing of former Serb-held areas of Sarajevo that have been turned over to the federation.

At issue? Uniforms.

It was agreed among the Muslim and Croat authorities that the Croats could wear blue uniforms, while those from Sarajevo would wear green uniforms until all federal police get gray uniforms now being made.

The uniform color remains the excuse for what is perceived to be a more profound disagreement over who controls what in Sarajevo.