Israeli Foreign Minister Moshe Dayan told his senior staff yesterday that "creeping occupation" by the Syrian Army in Lebanon could lead to the placement of Syrian missiles and Soviet advisers hard alongside Israel's border.

Dayan said the urgency of the situation in Lebanon, where Israeli-supported Christian militias have been under attack by the Syrians, will be conveyed to the "highest levels" of the U.S. government when the Israeli degelation to the Camp David summit meeting arrives in the United States on Sunday.

The warning by Dayan to his top advisers was related to reporters by a Foreign Ministry spokesman in what appeared to be an intensification of Israel's efforts to focus attention on Lebanon without appearing to threaten military intervention. The same warning, government officials said, was given to U.S. charge d'affairs Samuel Hart in a meeting Wednesday with Dayan, Prime Minister Menachem Begin and Defense Minister Ezer Weizman.

There apparently was no mention of military intervention in Dayan's remarks to his staff.

In a speech to the United Jewish Appeal here, Dayan said, "We are trying to political means to do everything we can and everything the big powers can to achieve a cease-fire in Lebanon and the status quo. Let's hope that will work out and let's not discuss a military move."

Warning of creeping Syrian occupation in Lebanon, Dayan was said to have told his staff that the Syrians could first he expected to seize control of Beirut by cutting the capital off from Phalangist and National Liberal Party militias in the hills to the north.

Then, they could move part of their army to the central region of Lebanon, possibly bringing in surface-to-surface missiles and Soviet advisers.

When asked whether Dayan's warning was conjectural or whether it was based on intelligence forecasts, the Foreign Ministry spokesman said, "It was pointed out as a possible aim. We are aware of the historical aim of Syria to take over Lebanon and establish a greater Syria. We know how Syria is slicing the salami."

In the Jewish appeal speech, Day an said, "Of course, we are concerned with Camp David, but we cannot ignore other things happening.

"As usual, at the time we do not appreciate probably enough the importance of such events. Only when you eventually read the history, then you think, 'You know what happened in 1978, Syria just moved in and took over Lebanon,' and at the time it just slips between your fingers."

He added," it is happing now - not in Czechoslovakia but here next to our door and it will have repercussions on our security."

Dayan also said the United States will be urged to consider the "humanitarian" aspects of the fighting in Lebanon and to consider that if the Christian militias are defeated, Lebanon will turn into a "slaughterhouse" of reprisals against Christian civilians. He was said to have reminded his staff that the plight of Christians "brings up to the memory of the Jewish people a very dary era of Jewish history."

The Foreign Ministry, meanwhile, said it had no knowledge of the Soviet Union issuing a warning, directly or indirectly, against Israeli military intervention in Syria, as suggested by the Hebrew daily Yedioth Aharonoth.

In another development, opposition Labor Party leader Shimon Peres met with Begin to discuss the government's preparations for the summit meeting and reported a number of points where he and Begin agreed on the limits of concessions.

These include, he told reporters, no return to the pre-1987 borders, no Palestinian mini-state on the West Bank of the Jordan River and the necessity of the Israeli Army remaining on the West Bank.

Peres' remarks reflected the unusualy unity among the political factions on the eve of the summit, with Begin's most vocal critics generally expressing support for the summit delegation after months of bitter dispute over Israel's peace policy. That debate led to presentation in parliament of a no-confidence motion in May on the Begin administration's foreign policy, a challenge which Begin easily withstood.

On the Syrian Army issue, Peres said yesterday, "We did discuss Lebanon and by and large, on the Lebanon issue there is a national policy." The National Religious Party, whose parliamentary faction assures the continuation of Begin's likud coalition, has also been generally supportive of the peace policy as the summit meeting approaches.