Israel and Lebanon began their first formal negotiations since 1949 here today and immediately fell into a public squabble over the legal state of their relations after the three decades of intermittent warfare in the Middle East since then.

With an American delegation headed by U.S. envoy Morris Draper looking on stoically, Antoine Fattal, the head of the Lebanese delegation and David Kimche, his Israeli counterpart, used the opening public ceremony to stake out what each country expects from the talks, in the process underscoring the differences in their initial bargaining positions.

Fattal made clear that Lebanon views the negotiations primarily as a means to achieve an Israeli troop withdrawal from its territory as part of an overall agreement for the withdrawal of Syrian and Palestinian forces as well.

Kimche, voicing Israel's more ambitious agenda for the talks, said he hoped they would produce an agreement that is "but a step away" from a formal peace treaty between the two countries.

The 40-minute opening ceremony was followed by more than four hours of private discussions. Spokesmen for the delegation said afterward only that the agenda was discussed, that "progress was made" and that the talks will resume Thursday in the northern Israeli town of Qiryat Shemona.

The talks, which opened amid heavy security, took place at the Lebanon Beach Hotel in this southern suburb of Beirut. Lebanese, Israeli and American flags decorated the entrance today.

In the meeting room, the delegations sat at rectangular tables arranged in the shape of a triangle, with the Lebanese at the base flanked by the Israelis on their right and the Americans on their left. Packs of American and British cigarettes and small dishes filled with nuts were placed on the tables, which were covered with blue cloths.

The direct Israeli-Lebanese talks are only one part of the efforts to remove foreign forces from Lebanese territory. Whatever agreements are reached between the Israelis and the Lebanese, their implementation will depend on the willingness of the Syrian and Palestinian forces also to leave Lebanon.

Israel has said it will not withdraw its troops unless the Palestinians leave the country first and the Syrians agree to leave simultaneously with the Israelis.

As the private negotiations were going on today, state-run Israeli radio reported that a deadlock had developed over Israel's insistence that political relations and security arrangements be discussed before the details of a troop withdrawal.

The differences over what the negotiations are to be aimed at have existed throughout the weeks of effort that had culminated in today's opening session and are likely to dominate the early stages of the talks.

Israel, whose army occupies the southern third of Lebanon, is clearly in the stronger bargaining position and has vowed it will not agree to a troop withdrawal without also gaining Lebanese agreement to the beginning of normal relations between the countries and the establishment of a 25- to 30-mile-wide "security zone" in southern Lebanon to protect its northern border.

The negotiations, which began six months and 22 days after Israel invaded Lebanon, took place in a second-floor room overlooking the Mediterranean. In a reminder of the conflict that still afflicts Lebanon, Israeli troops roamed the mountains to the east, where there have been recent clashes between Lebanese Christian and Druze militias.

To the northwest, U.S. Navy warships could be seen off the coast of Beirut where a contingent of U.S. Marines is serving as part of the multinational peace-keeping force.

Fattal, a former director-general of the Lebanese Foreign Ministry, opened the brief public ceremony attended by the three six-member delegations. Although it had been announced that the opening statements would be in English, the language the negotiations were to be conducted in, Fattal said he would speak in French "because I am a French speaker." His remarks were later translated into English by another member of the Lebanese delegation.

Setting the stage for what would bring a politely diplomatic rejoinder from Kimche, Fattal said Lebanon considers the armistice agreement it reached with Israel on March 23, 1949, still in force.

"Lebanon did not declare war against Israel in 1967," he said. "Lebanon did not resort to any belligerent action against Israel. We deem it important to remind all concerned here that the Palestinian presence on our territory was at the origin of serious troubles here and elsewhere . . . . We did not want it nor provoke it."

The implication was that the Lebanese see no need for further agreement on "normal relations," a topic Fattal did not allude to in his statement. "I cannot be held responsible for the decades of Palestinian-Israeli conflicts."

He said Lebanon's objective for the negotiations was to regain its sovereignty and authority in its own territory and to see the withdrawal of all foreign forces "on an accelerated schedule."

Fattal also indicated Lebanon's reluctance to become the second Arab country after Egypt to reach a formal peace treaty with Israel. He said "Lebanon shall not undertake alone any action which may prejudice the extension of the peace process and security in the region.

"Nor will Lebanon accept to jeopardize . . . the fulfillment of the historic mission it has set for itself in the Arab world," Fattal said. "Furthermore, my delegation believes that it is in the interest of all concerned that Lebanon's traditional role as mediator should be safeguarded."

Kimche, who scribbled notes as Fattal spoke, departed from his prepared statement to say that he wished to "take the honorable head of the Lebanese delegation to issue on the question regarding the armistice agreement."

Kimche, the director-general of the Israeli Foreign Ministry, said that just before the 1967 war Lebanese leaders "declared their association with Arab armies" that were attacking Israel and refused to meet with Israeli representatives. After the war, Kimche said, Lebanon signed various agreements that allowed the Palestinians "to operate freely from Lebanese territory against Israel in complete violation of the armistice agreement."

"We therefore consider that these acts terminate de facto the armistice agreement," he said.

But more important, Kimche added, "the new relations which we wish to see evolve from the negotiations which begin today will in every sense of the word supersede those armistice agreements . . . which will become in our eyes completely null and void by the agreement that we hope to sign here, an agreement which we believe will be but a step away from the full, final, formal peace treaty that we would like to see come about."

Kimche said the Israelis have "no feelings of enmity" for Lebanon and invaded the country on June 6 only to destroy the Palestine Liberation Organization, whose presence he said "made a mockery of Lebanon's independence and sovereignty."

"The political and military infrastructure which the terrorists had established posed a danger both to the Lebanon and to Israel which had to be removed for the well-being of our two peoples."

Draper was the last of the delegation heads to speak. Declaring that there is "a good basis for confidence that the negotiations will be productive," the U.S. envoy said, "The United States believes strongly that legitimate security interests of Israel should be addressed and satisfied to the maximum extent possible. At the same time, the United States supports Lebanon's independence, national unity and integrity, and the restoration of full sovereignty throughout its territory."

The American role in the talks is among the points of difference between the Israelis and the Lebanese. Lebanon has insisted on full U.S. participation in the negotiations, but the Israelis have downplayed the American role, describing it as that of observer.