U.S. Secretary of State Colin Powell called Prime Minister Ariel Sharon last night to discuss the level of Palestinian warfare against Israel. Sharon said that given the current violence, negotiations with the Palestinians cannot be resumed. Israel sent a detailed letter about the exchange of fire initiated by Muhammad Dahlan\'s agents against Israeli soldiers this past Thursday. The letter contains an expression of \"regret\" over the incident, however, because it cannot be ascertained 100% that those who initiated the fire were actually Dahlan\'s agents.