Israeli Defense Minister Moshe Arens today accused the Lebanese government of not working hard enough to find a political solution to the warfare between Christian and Druze militias in the mountains near Beirut, but he said the fighting would not delay a planned Israeli troop pullback.

Arens, on a surprise visit here, told reporters that Israel intends to go ahead with its planned withdrawal from the Chouf Mountains, the site of the recent heavy fighting, "in the near future," but he would not specify a date.

In Tel Aviv, however, Lt. Gen. Moshe Levy, chief-of-staff of the Israeli Army, told reporters that the pullback from the Beirut suburbs to new lines at the Awwali River 18 miles to the south would take place "in a matter of days." He also said it would be done in one swift movement rather than gradually, Washington Post correspondent Edward Walsh reported.

Previously, Israeli military officials had spoken of completing the partial pullback by November, before the onset of winter weather, and they had indicated it would be in phases, to allow the Lebanese Army to move into the evacuated territory slowly while testing its ability to police the areas.

Levy said the Israeli pullback would take place as planned whether or not an agreement is reached to end the fighting between the Lebanese Christians and Druze in the Chouf Mountains southeast of Beirut that Israel intends to evacuate.

He, too, refused to give the date of the planned pullback, but he said that "we count it in days." He added, "I think it is best to do it not in stages, but in one piece."

The Israeli pullback, designed to reduce casualties and the cost of maintaining the Army in Lebanon, will involve the evacuation of about 370 square miles of territory held by Israel since its invasion a year ago, including the southern outskirts of Beirut, the Beirut-to-Damascus highway and the Chouf. Israel is planning to assume new positions along the Awwali River north of Sidon, where it has said it intends to remain until Syria and the Palestine Liberation Organization agree to withdraw from northern and eastern Lebanon.

Arens talked to reporters in the Christian eastern sector of Beirut, after a visit to his officers at a sandstone villa on a hilltop overlooking Lebanon's Defense Ministry that Israel uses as offices for its diplomats and Army spokesman.

Later, he drove to the headquarters of the Lebanese Forces, the main Christian militia, which worked closely with Israel in the early months of the invasion, laid a wreath on their "Martyr's Grave" and met with the militia's command council.

Offering Israel's "good offices" to help prevent further "bloodletting," Arens stressed, nevertheless, that Israel intends to go ahead with its pullout from the mountains. Privately, Lebanese and Israelis express the fear that the Israeli Army might leave in less than a week and that the factional violence could spread.

"The deployment of Israeli forces, as I'm sure you understand, is motivated primarily, I would say solely, by Israeli defense interests," Arens told reporters, "and therefore we cannot make the movement of our troops contingent upon arrangements that may or may not be reached in the area."

Israel has said it is withdrawing from the mountains to positions more secure from guerrillas. Since the invasion in June 1982, 516 Israeli soldiers have died in Lebanon and 2,932 have been wounded, according to Israel military spokesmen.

Arens said, "I hesitate to voice any strong opinions about the internal politics of Lebanon but it is the impression or, if you will, the concern of the people in Israel that the Lebanese government should be putting greater emphasis on trying to reach a political accommodation between the Christian and Druze communities."

He spoke warmly about the Druze in Israel, who he said were concerned about their coreligionists in Lebanon. He rejected as "baseless" the charge by Lebanese, foreign diplomats here and some of the Israeli press that Israel had aided and manipulated both sides.

Arens did say that his "guess is that there may be a trickle" of light arms to Druze forces from Syrian territory behind Israeli lines.

Asked why the Israelis have not stopped Druze missiles from being fired at the Beirut International Airport from Israeli-controlled areas, Arens responded:

"That's easier said than done. That's certainly something we would like to do. . . . But there is a significant quantity of arms in the area and it is very difficult, I would say impossible, to bring about a total cessation of activities of some of the military units in the area."

As Arens visited Beirut, the city's airport reopened after being closed for six days, following a heavy Druze rocket attack last Wednesday and threats of more shelling unless the Lebanese government met Druze demands for a redistribution of political power.

The agreement to reopen the airport came after frenzied negotiations yesterday including envoys of Saudi Arabian King Fahd and King Hussein of Jordan.

The details of the terms of the accord permitting planes to land without fear of renewed shelling were not disclosed. Lebanese officials said they hoped to have the airport in full operation Wednesday.

Meanwhile, U.S. Marine Commandant Paul X. Kelley, who visited his forces in the multinational peace-keeping force here, told reporters that he did not expect the U.S. Marines to move into the mountains to assist the Lebanese Army after Israel withdraws.

"There is always the possibility, but I think that would require a change in mission," Kelley said. "I don't see a change in our mission at this particular time."

Walsh reported from Tel Aviv:

Levy, responding to questions, dismissed suggestions that the Lebanese Army is incapable of taking over the Chouf. He said they could do it "easily" if they went about it "in the right way," and he criticized the Lebanese for "hesitating" to move against the warring Christians and Druze.

Levy also dismissed suggestions that Israel, by introducing Christian forces into the Chouf after its invasion, has some responsibility for the renewed fighting there. He said Lebanon has had internal problems for "hundreds of years."

Levy, who took over command of Israeli forces in May, said Israel does not intend to construct a fence along the new Awwali River line and said the amount of Lebanese farmland that will be uprooted as a result of building new fortifications will be "on a very small scale."