JENIN, West Bank?From a West Bank army base overlooking the scene of the deadliest fighting in Israel’s 13-day-old offensive, Prime Minister Ariel Sharon on Wednesday delivered a blunt message: Israel will not pull back until Palestinian militias are crushed.

Sharon’s statement defied increasingly impatient U.S. demands for a withdrawal from Palestinian towns?to be delivered in person Friday by Secretary of State Colin Powell?and came hours after an Islamic militant blew himself up on a bus in northern Israel, killing himself and eight passengers.

Speaking to soldiers near the Jenin refugee camp, Sharon said he explained to President Bush that “we are in the middle of a battle” which, if abandoned prematurely, would only require another round of fighting later on.

Powell insisted his peacekeeping mission was not threatened by Sharon’s refusal to halt the incursions.