In a lightning-fast operation using army helicopers, Israel established a new civilian settlement today on a stony hill overlooking the Arab town of Nablus - the first Jewish outpost since the signing of the Egyptian-Israeli peace treaty.

The settlement, approved Sunday by the Israeli Cabinet in the face of vehement opposion by the United States and Egypt, became a fait accompli by nightfall, with the Israeli flags flying in a compound of a half dozen tents alongside this tiny Arab village about two miles southeast of Nablus.

The use of Army helicopters and troops to guard the operation seemed to underline the Israeli policy of continuing its West Bank settlements, which the United States said Monday is "harmful to the peace process" and particularly regrettable at the beginning of negotiations between Egypt and Israel on autonomy for the area.

Officials of Gush Emunim, the ultranationalist organization that will form he nucleus of the new Elon Moreh settlement, and members of the World Zionist Organization said 1,000 settlers will move into the settlement in the first stage. Gush Emunim envisions an urban complex reaching 100,000 persons within 10 years - twice the size of Nablus itself.

But in its first night, Elon Moreh was little more than a rustic campsite of pitched tents on a windswept hillock heavily guarded by Army troops who kept strangers and curious Arab children at a distance.

Villagers talked excitedly about "the machines" that had been cutting a new roadway to the settlement, pointing to earthmovers and bulldozers parked alongside army tents.

Earlier in the day, helicopters landed the vanguard of the settlers and their protective army escort, bringing in barbed wire for a perimeter fence and generators and water tanks to sustain the nucleus until the new road is completed.

Immediately before work began on a new road, requisition orders for several hundred acres of Arab-owned uncultivated land were handed to their owners by military officials.

Among the first airlifted arrivals at Elon Moreh was Agriculture Minister Ariel Sharon, who told the settlers the timing of the construction was important "because it goes in the face of" opposition raised by critics of Israel's West Bank settlement policy.

Sharon announced to the group that the government had "proved its credibility" inside and out of Israel, and had demonstrated dramatically its right to settle in all parts of Eretz Israel - the biblical term applied to Israel proper and territories occupied in the 1967 six-day war.

The new settlement will be established by Gush Emunim's Elon Moreh group, which has been waiting for almost three years near the former Jordanian army base at Kadum for government permission to move here. In September, Gush Emunim almost caused a government crisis by establishing an illegal settlement near this site until the army forcibly removed 150 of its members from their makeshift quarters.

Gush Emunim officials said tonight that women and children will be taken into Elon Moreh Friday morning "to make permanent" the new outpost.

Settlement opponents, however, reacted sharply tonight to its creation.

Opposition Labor Party members of parliament said the joint Gush Emunim-army operation was "another setback" for autonomy plans for West Bank Palestinian residents. They vowed that the Labor Party will introduce a motion in parliament against the move.

The Peace Now movement, which has persistenly opposed the Likud government's settlement policy, said it would wage a new campaign against further Jewish civilian outposts in the occupied territories.

Elisas Khouri, an Arab attorney long active in land cases in the West Bank, said he will file an appeal in the Israeli Supreme Court to stop the Elon Moreh settlement.

Deputy Prime Minister Yigael Yadin, who along with Defense Minister Ezer Wezman and Foreign Minster Moshe Dayan, voted against approval of the Elon Moreh outpost, said he had done everything he could to block the move, but that the settlement had won a majority of the Cabinet. CAPTION: Map, no caption, By Dave Cook - The Washington Post