The Arab summit conference opening in Morocco on Wednesday will be the first regional test of a new activist Saudi diplomacy that seeks a public leadership role for the kindgom among its peers in the Arab world.

Central on the agenda will be discussion and, the Saudis hope, unanimous approval of the eight-point Middle East peace plan presented in August by Crown Prince Fahd. Already a number of Arab states -- Syria, Libya, Algeria, Iraq and South Yemen -- have attacked or indicated doubt about the plan, which implicitly calls for recognition of the state of Israel.

Whether or not the Saudis win a gamble on which they have staked much of their prestige and influence, the mere existence of the plan under Saudi sponsorship and the open lobbying the kingdom has undertaken on its behalf mark a major shift in Saudi policy and diplomatic style.

"Viewed from the history of Saudi diplomacy," remarked one Western diplomat, "this is a new chapter."

The Saudis' choice of this moment in the Middle East conflict to make the proposal and the fact that the traditionally cautious royal family managed to agree on such a sensitive issue reflect the perception here of the Arab world standing at a crossroads and faced with the desperate need for a workable alternative to the U.S.-sponsored peace process.

Israel has vehemently condemned the Fahd plan, saying that it provides no recognition of the Jewish state and, if acted upon, the eight points "will lead to the annihilation of Israel by stages, as preached by the PLO."

The Israeli government has described the plan as "reflecting no departure whatsoever from Saudi Arabia's traditional negative and hostile policy toward Israel," and said it must be "totally rejected by all those interested in advancing the cause of peace" in the Middle East.

Ever since the late Egyptian president Anwar Sadat broke with his Arab colleagues to deal directly with Israel and sign a peace treaty, the rest of the Arab world has stood in opposition but without presenting any other acceptable plan.

Only a year ago, the Saudis themselves were calling upon all Arab states to launch a jihad, or holy struggle, against Israel.

Now, Fahd, the kingdom's day-to-day ruler and author of the jihad appeal, has publicly recognized the need for a credible Arab negotiating position to serve as an alternative to the faltering Camp David process.

In an interview with the Saudi News Agency early this month, Fahd provided what is still probably the best official explanation for why the kingdom decided to act when it did as well as press for the adoption of the plan as an all-Arab position at the summit in Fez, Morocco.

He noted seven factors, the first of which was the presence of Sadat in Washington last August to revive the stalled Camp David negotiations. Others included Israeli military strikes into Lebanon and Iraq plus the Israeli-Syrian missile crisis in early summer making "the whole situation quite explosive in the region;" the reelection of Begin as prime minister and the appointment as defense minister of Ariel Sharon, whom Fahd called an "adventurer militarist" favoring more Israeli settlements in occupied Arab lands.

Fahd also noted the new phase in U.S.-Israeli military coordination as reflected in the talks held in Washington between President Reagan and Begin in September on closer strategic cooperation.

At the same time Fahd said the central objective of the plan was to present Washington with an alternative to the Camp David accords "so balanced and reasonable" as to convince the authors of the American-sponsored peace process "that there could be another peace framework radically different from Camp David and worthy of attention, meditation and perusal."

But Fahd clearly was speaking as much to fellow Arabs as to the West. One of the criticisms leveled against the Saudis, in private if not in public, was that they had broken an earlier Arab pledge that none of them would take a unilateral initiative as Sadat had done without first consulting the others.

Diplomatic observers here believe the Saudis acted to press their plan with such unusual vigor in part out of fear that the continuing unsettled Middle East situation was bound to favor Arab radicalism and undermine the region's moderates, most notably Saudi Arabia itself.

With their unexpected initiative, the Saudis seem to have miffed some Arab leaders by failing to consult beforehand and presenting them with a plan that does implicitly what they earlier criticized Sadat for doing explicitly, namely recognizing and opening negotiations with the state of Israel.

But a recognition of a vacuum in the Arab world and Saudi fears that the region's radicals would step in to fill it if they did not, do not fully explain the sharp internal break with the long Saudi tradition of backroom maneuvering rather than risky public diplomacy.

Western analysts here trace the beginning of the new Saudi activist policy to early this year when the kingdom took over the presidency of the 42-nation Islamic conference. Then in the spring and summer, Saudi Arabia played a major role first in helping the United States avert a crisis between Israel and Syria over the stationing of Syrian missiles in Lebanon and then in getting the Arab League reinvolved in the search for a solution to the internal Lebanese political turmoil.

Following these diplomatic successes, the kingdom again demonstrated its growing economic and political clout by forcing the Organization of Petroleum Exporting Countries to lower the price of oil to levels dictated by Saudi Arabia.

But OPEC, to the kingdom's secretive collegial-ruling family, is a far safer forum in which to vie for leadership than the regional minefield of the Palestinian issue.

How the royal family, whose decision-making process is tortuously slow and little understood by outsiders, came to a consensus on the Fahd plan is something that outsiders can only speculate about.

So far as is known in Western diplomatic circles here, there was no major dissension within the ruling family over the plan which, it is presumed, had to be thoroughly discussed before its publication so as to have a consensus on such a risky diplomatic venture.

The one outside leader who may have been apprised of the plan and whose views may have been solicited is Yasser Arafat, the PLO chief, who visited here in late July for secret talks with the Saudis.

Arab and Western analysts here note he was among the first Arab leaders to come out in guarded support of the plan and since then has repeatedly praised it.

Significantly, as the summit approaches, the Saudis have softened their sales pitch, saying it is not really a "plan" at all but merely a set of "principles" open for amendment.

"It is for the Arab world in general to discuss and we are waiting to see the judgment of other Arab countries," Saud said at a press conference here last week.

The summit "judgment" promises to be not only on the Fahd plan but also on the new activist Saudi diplomacy in the Arab world.