The breakup yesterday of the Arab summit in Fez, Morocco, over Saudi Arabia's eight-point peace plan is being viewed by Israeli officials as a vindication of Israel's oft-stated argument that Saudi Arabia is not a major political factor in the Middle East and that the Arab world is incapable of collectively coming to terms with the existence of the Jewish state.

At the same time, Israeli foreign policy makers, revealing a certain ambivalence over the summit fiasco, said the Arab disarray appeared to have strengthened the rejectionist front, and in particular Syria, at the expense of Israel's long-term national security interests.

A senior government official, in a background briefing on the implications of the summit, said, "The lesson for Israel is that even if you have a plan along the extremist Arab line, still this is not good enough to be the basis of a collective agreement. It is a vindication of the line that we have taken, that you cannot deal with the Arabs collectively."

For several months, the government of Prime Minister Menachem Begin has been showing increasing concern over the prominence Saudi Arabia has attained in the West, particularly in the United States, as a potential moderating factor in a future comprehensive solution to the Arab-Israeli conflict.

This concern began to grow amid reports of a strong Saudi influence in achieving a breakthrough in the July Israeli-Palestinian cease-fire in southern Lebanon, and peaked last month when the Reagan administration expressed interest in the eight-point Saudi peace proposal. That plan calls for Israeli withdrawal from the remaining territories occupied in the 1967 six-day war and the creation of a Palestinian state in Gaza and the West Bank, including East Jerusalem, along with guarantees for the states of the region to exist in peace.

Begin and other Israeli leaders have maintained that U.S. perceptions of Saudi Arabia as a potentially major diplomatic force in the region were misguided, and that Saudi Arabia is an impotent, unstable force in the Arab world.

"They the Saudis put a lot of energy into that peace plan, with visits, cajoling and promising here and there. It was unprecedented. For them, this is a setback. It demonstrates what you can and cannot get out of Saudi Arabia," the senior official said.

He added, "Saudi Arabia is just not a strong country. We have been saying that all along. It has lots of money, oil and real estate, but it obviously is not held in great respect by the other Arab countries. It has no political clout. Fez showed in a real measure what they can't achieve."

When asked which was his stronger feeling, that of satisfaction over Saudi Arabia being politically weakened or that of concern at Syria gaining strength within the rejectionist front, the Israeli official replied, "I wouldn't speak in terms of satisfaction or glee. For us it is a matter of analysis of what happened in Fez."

The official said that Egypt, Israel's new ally, had been strengthened because of the general weakening of Arab unity apparent in Fez.

The official rejected the notion that a broader solution to the currently dormant crisis over Syrian missiles in central Lebanon would be harder to achieve because the Saudis had suffered a major political setback at the hands of Syrian President Hafez Assad. "Our position is that the Saudis did not play a key role in obtaining the Lebanon cease-fire. They meddled with money, but United States intervention was the most important factor," the official said. He added that the Fez setback for Saudi Arabia should not affect the upcoming mission of U.S. special envoy Philip C. Habib.

The Israeli official also dismissed suggestions that the Arab world perception of point seven in the Saudi plan -- the right of the states of the region to exist in peace -- was that it was intended to tacitly acknowledge the legitimacy of the state of Israel.

Israel has long maintained that point seven was never intended to condone the existence of Israel.

The official said Arab rejection of the Saudi plan was not proof that Saudi Arabia intended to recognize Israel. "That wasn't the only reason the plan did not get acceptance. They didn't want to come to terms with Israel in any way," he said.