ZAMBOANGA, Philippines (AP) _ A Muslim extremist leader phoned a local radio station Monday to say he will kill at least one American hostage that day unless the government appoints two Malaysians to negotiate their release.

Abu Sabaya, leader of the Abu Sayyaf extremist group, had on Thursday threatened to kill a Californian and a Kansas couple, setting a vague deadline. This was the first time he actually set a time _ noon, local time, on Monday. That deadline is at midnight Sunday, EDT.

Asked whether he will kill an American or a Filipino hostage, he said : ``I will make sure it will be a white.'' The group is believed to be holding 13 captives; three Americans and the rest Filipino.