Israel pressed its sweep through the West Bank Friday in search of Palestinian militants and warned it was ready to use force if necessary to end a standoff at the Church of the Nativity.

The Israeli government, meanwhile, prepared for the weekend arrival of a UN fact-finding mission into the fierce fighting at Jenin refugee camp but said minor issues had to be resolved before the team was allowed on site.

Israeli troops backed by 15 armored vehicles and two helicopters pursued their nearly month-old West Bank offensive, launching a pre-dawn incursion into the town of Qalqilya and detaining up to 20 Palestinians, the army said.

The militants, suspected of taking part in anti-Israeli attacks, were picked up in Qalqilya as well as three villages between the towns of Nablus and Jenin, a spokesman said.

Witnesses said two local leaders of the radical group Hamas were detained in Qalqilya, and 10 people linked to the Palestinian security forces or YASSER ARAFAT'S Fatah movement were arrested near Jenin.

The army forces withdrew from Qalqilya on April 9 after occupying it under Operation Defensive Wall launched on March 29.

Israeli Defense Minister Binyamin Ben Eliezer said during an inspection of troops in the area that the incursion was a "short-term" operation and not a re-occupation of Qalqilya, army radio reported.

He said the forces moved on information that new anti-Israeli attacks were being prepared at Qalqilya, not far from the suburbs of Tel Aviv.

In Bethlehem, where three days of negotiations have failed to evacuate about 200 Palestinian gunmen holed up inside the Church of the Nativity, an army commander cautioned that the sitation "is not open-ended.

"If we have to exercise a military option, we will," Captain Joe Leyden told reporters.

The military had previously ruled out storming the church, which marks the birthplace of Jesus, amid repeated Vatican appeals for Israel to end the siege. TWO ISRAELI SOLDIERS LOOK AT A GROUP OF PALESTINIAN TEENAGERS WITH MASKS IN FRONT OF THE DOOR OF THE CHURCH OF THE NATIVITY ON APRIL 25, 2002, AS THEY WAIT FOR PERMISSION TO TAKE OUT TWO CORPSES THAT PALESTINIAN MILITANTS SAY HAVE BEEN IN THE COMPOUND FOR MORE THAN THREE WEEKS. THE BODIES OF TWO PALESTINIANS KILLED IN FIGHTING TWO WEEKS AGO WERE BROUGHT OUT ALONG WITH NINE YOUTHS IN WHAT WAS THE FIRST LARGE-SCALE RELEASE OF PEOPLE FROM THE 1,700-YEAR-OLD CHURCH. PHOTO: OLEG POPOV

The chief Palestinian negotiator in Bethlehem had threatened to boycott further talks unless Israel released nine Palestinians youths who left the complex Thursday accompanying the bodies of two men killed by gunfire.

Eight of the nine were released after questioning about their possible participation in any anti-Israeli attacks and the situation inside the church, according to the negotiator, Salah al-Taamari.

Fuad al-Laham, 19, was handed over to Israel's domestic security agency Shin Beth for further questioning, Taamari said.

The negotiations have stalled over Israel's refusal to accept a Palestinian proposal to evacuate all the gunmen to Gaza and the Palestinians' rejection of an Israeli proposal that they face either exile or trial in Israel.

No new talks were scheduled Friday. Taamari said he had received Israeli authorization to visit Arafat on Saturday in his besieged base in the town of Ramallah to brief him on the negotiations.

While residents of the Jenin refugee camp on the northernmost West Bank continued to dig out of the rubble, Israeli officials awaited the arrival of a UN fact-finding team that will look into the nine days of fierce fighting.

Government spokesman Avi Pazner confirmed that major issues brought up with UN Secretary General Kofi Annan were resolved during a series of meetings in New York but minor points remained to be settled.

"We know that the team will be coming (to Israel) over the weekend; we don't know exactly on which day," Pazner told AFP.

Israel had originally given its approval to the mission but balked amid fears it would focus on the destruction at Jenin and ignore concerns the camp had been turned into what the Israelis call a haven for terrorists.

Pazner said Israel wants to make sure that the team arriving here "remains a UN fact-finding mission and not one that makes any conclusions. TWO ISRAELI SOLDIERS RUN FOR COVER AFTER OPENING A SMOKE CANNISTER, AS THE ISRAELI ARMY TRIES TO PREVENT MEMBERS OF THE INTERNATIONAL MEDIA FROM TAKING PICTURES IN FRONT OF THE CHURCH OF NATIVITY, APRIL 25, 2002. NINE PALESTINIAN YOUTHS AND TWO CORPSES WERE BROUGHT OUT OF BETHLEHEM'S BESIEGED CHURCH OF THE NATIVITY AND FRESH TALKS WERE EXPECTED ON THURSDAY TO RESOLVE A THREE-WEEK-OLD STANDOFF AT THE SHRINE. PHOTO: GORAN TOMASEVIC

"We want them to investigate the terrorist activity in Jenin, and we want them to guarantee immunity for the (Israeli) soldiers" involved in the intense nine-day battle in the northern West Bank camp, he said.

Among the issues to be clarified, Pazner said, was the status of the military and anti-terrorism experts accompanying the UN mission whom Israel wants upgraded from advisers.

"The negotiations are not over," he said. Asked whether Israel has given its final permission for the team to enter the camp, Pazner replied: "Not yet."

Meanwhile, the head of Amnesty International, Irene Khan, is to visit the Jenin camp on Sunday to assess the situation there, the rights group's director in the Gaza Strip, Farid Hamdan, told AFP.

Amnesty called on Monday for an international war crimes probe into the events surrounding the Israeli invasion of Jenin.

On the diplomatic front, US President George W. Bush welcomed Saudi Crown Prince Abdullah bin Abdul Aziz to his Texas ranch Thursday where the two leaders spoke of their shared "vision" for Middle East peace.

But a key Saudi aide warned of "grave consequences" if Washington did not moderate its support for Israel.AFP