The Lebanese Army and the Druze and Moslem militia groups it has been battling for the past month met today to discuss ways to consolidate the increasingly shaky cease-fire that went into effect Monday.

Despite an apparently positive first meeting of the security committee, there were reports of small clashes here and there across the country, raising fears that the three-day-old cease-fire was already in danger of falling apart.

In addition, the Druze militia put out a statement saying it would not allow Beirut International Airport to reopen Thursday as planned, charging that this would be a "serious violation" of the cease-fire. Public Works Minister Pierre Khoury then said the airport would remain closed until the security committee worked out arrangements for its reopening.

The news dealt a serious blow to Lebanese hopes for a quick return to normalcy here in the capital.

In the north, there was more fighting in and around the Baddawi Palestinian refugee camp outside Tripoli, where 600 guerrillas loyal to Palestine Liberation Organization chief Yasser Arafat arrived from the Bekaa Valley. But sketchy reports reaching here indicated that there was less fighting than yesterday, when at least 20 Palestinians were killed and 17 wounded in a shootout between pro- and anti-Arafat groups.

The first meeting of the security committee overseeing the cease-fire was finally held in an abandoned bank building in no-man's land just south of the capital after the four factions failed to agree on a site yesterday.

Soldiers of the 100-man British contingent of the multinational peace-keeping force provided security for the two-hour meeting which brought together the Army, the Christian Phalangist militia and the opposing militias of the Druze and the Moslem Shiite Amal organization.

Afterward, Phalangist representative Jean Ghanem said the meeting had been "very good," while Amal leader Nabih Berri said all sides had shown "good faith and good intentions." The committee agreed to set up a liaison center to deal with alleged violations of the cease-fire.

The meeting was held between the Druze town of Shuwayfat and the nearby Phalangist-controlled village of Kfarchima. But the next session will be held at another site, as yet undecided, participants said.

Shortly after the meeting broke up, Army positions at nearby Khaldah came under mortar fire and later Druze positions in the hills east of Khaldah also were shelled, either by the Army or Phalangist militia batteries.

There were also reports of fighting between the Phalangist and Druze militias further south in the Kharroub region around Barja and of renewed sniper fire in the southern suburbs of the capital.

The most depressing news to Lebanese today, however, was the position taken by Walid Jumblatt's Druze-led Progressive Socialist Party that the reopening of the airport would not be tolerated.

A party declaration said that the government had used the airport for military purposes during the fighting and warned that it would reply "in strength and firmness" to any attempt to get it functioning again.

"Strict orders have been given to all military sectors and units to reply promptly to any attempt of this kind," it continued.

In Damascus, an aide to Jumblatt said the Druze militia would oppose any reopening of the airport until "a comprehensive security solution is reached." He warned international carriers not to land here "for the sake of the security of their planes and passengers."

Despite today's developments, Middle East Airlines president Selim Salam insisted that "nothing has changed" in plans to resume airport operations Thursday. Hundreds of Lebanese and foreigners bought tickets today and Middle East Airlines reportedly scheduled nine incoming flights on the first day.

Meanwhile, the government today continued intensive discussions about arrangements for moving neutral observers into the battle zones to oversee the cease-fire and about holding the first meeting of the proposed national reconciliation conference of Lebanon's leading political and sectarian figures.

Western diplomatic sources said the question of obtaining United Nations observers was being discussed in New York but that Syrian and Soviet objections to the makeup of the corps still had to be overcome. There are apparently also questions about the involvement of French and Italian soldiers from the multinational peace-keeping force in the mountain battle zones.

Government efforts to arrange the reconciliation conference centered today on a plan for the quick formation of a new national coalition government grouping the main political factions to fashion a new power-sharing formula among Lebanon's 17 ethnic and religious communities.

Under this plan, an initial meeting of the national reconciliation conference would be held abroad, probably in Saudi Arabia, to reach agreement on broad principles of a settlement, while the details of a new formula would be worked out by the new coalition government.

President Amin Gemayel was said to favor this plan, which would reduce direct Syrian influence in the discussions because they would take place inside Lebanon under the auspices of the Lebanese government.

Both Syria and Saudi Arabia were to participate in the reconciliation conference as "observers" but the Gemayel government fears that Syria in particular will try to dominate the discussions and dictate a solution.

It was not known here tonight, however, whether leaders of the Syrian-backed opposition National Salvation Front--Jumblatt, former president Suleiman Franjieh and former prime minister Rashid Karami--would go along with this plan.

Both Jumblatt and Franjieh said today that they would participate in the reconciliation conference but another invited leader, Raymond Edde, who lives in self-imposed exile in Paris, said he would not come back until all Syrian and Israeli troops had left Lebanon.

Western diplomatic sources said here today it was imperative to get Lebanon's political elements together as quickly as possible before the situation on the ground deteriorate and positions harden.

Meanwhile, Arafat supporters at Tripoli's Baddawi refugee camp gave a warm welcome to 600 guerrilla loyalists who arrived there today. It was not clear whether they were part of the group of 1,000 to 1,500 guerrillas encircled by Syrian security forces in the Hermel mountains north of the Bekaa Valley last weekend.

Just before the cease-fire, Syria decided to remove all pro-Arafat guerrillas in the Bekaa to Tripoli in what appears to be a final move to crush his last remaining forces in Lebanon.