The best chance in 30 years for a negotiated settlement to the Arab-Israeli dispute has evaporated almost completely despite the intensive efforts of President Carter and Secretary of State Cyrus Vance.

If a diplomatic deadlock sets in, as appears likely, it could create conditions for political upheaval, guerrilla activity, border clashes and, eventually, a fifth Middle East war.

U.S. stakes in the region, now greater than ever, would be directly threatened. Washington's improved relations with Egypt and Syria since the 1973 war - based on the premise in those two countries and in Congress of a momentum toward regional peace - would be undercut. Far more eminous is likely damage to relations with Saudi Arabia, on which the United States and the rest of the developed world are deeply and increasingly dependent for oil.

This sounds like a nightmare scenario - and it is - but a 11-day Middle Eastern journey aboard Vance's airplane leaves me no cause to expect anything much better. The stringing out of official hopes and pretenses through a diplomatic going-through-the-motions at the United Nations or elsewhere is not likely to impress anyone for long. A belief that something will turn up to save the day is a slender base for comfort in the Middle East, where the surprise are often unpleasant.

The roots of the present problems are embedded in the historic clash of perceived rights and wrongs which is the Arab-Israeli dispute. But the immediate cause of trouble is not obscure: it is the determined and fundamental rejection by Israeli Prime Minister Menahem Begin and his Likud government of the comprehensive Middle East bargain backed by the United States and world opinion.

The bargain - is developed out of the 1967 war, its diplomatic aftermath and the subsequent rise to world acceptance of the Palestinian problem - was codified by a Brookings Instution study group in December 1975 and publicily adopted early this year by the Carter administration. It calls for phased withdrawal by Israel from nearly all the territory it captured on 1967 and a form of self-determination for the Palestinians on the West Bank of the Jordan River in exchange for an end to hostilities and increasingly normalized relations with Israel on the part of the Arab States.

As the first nine days of Vance's trip made clear, the Arab countries around Israel accept the broad outlines of the comprehensive deal, but they are far from agreed among themselves or with the United States on many of the crucial details.

Egyptian President Anwar Sadat's crumbling power base at home probably can only be shored up by quick and convincing progress toward peace. Sadat has made clear through his controlled press that he objects to the gradual nature of the Israeli withdrawal proposed by the United States. For Syrian President Hafez Assad. who is more secure, the principle of complete withdrawal from occupied land is reported to be far more important than its timing.

There is disagreement among the Arab states on both the timing and nature of future arrangement between Jordan and the West Bank Palestinians. The Palestine Liberation ideas and unlike Egypt, Syria, Jordan and Saudi Arabia, is not yet ready to accept the existence of Israel within its 1967 borders.

Nearly all the Arab leaders resist the idea of cordial relations with their long-time enemy. The basic Arab desire, according to Western diplomats, is to ignore Israel as much as possible once diplomatic settlement is reached. A Jordanian diplomat conceded the topic of cross-border trade and travel, which exists in limited form today but said the long-term relations of Jordan and Israel should be about as close as those of Jordan and Denmark.

For all its variation from the U.S. ideal the shift in the position of Arab government toward Israel is impressive.

If they'd been talking this way 10 years ago we could have had a settlement after the '67 war," said veteran U.S. official.

Equality impressive is the seriousness of purpose sophistication and attempts at coordination displayed by Arab leaders during Vance's tirp. In every Arab capital, Vance was told that the principles of a comprehensive deal should be given priority over the knotty question of PLO representation.

"Unless there is the intention [in Israel] to solve problems, it is just useless to go to Geneva," said a senior Saudi diplomat. "Nobody wants to go there just to restate old problems. If that is the case, what is the point of going there?"

Even Sadat is reported to have cooledto a Geneva conference unless there is advance assurance that Israel will bargain seriously calculating that an early failure at Geneva would be no better - and far more trouble to arrange - than not going at all.

On the Israeli side the unexpected election victory of Begin and his Likud Party in mid-May has hardened both official and public attitudes against fundamental elements of a comprehensive deal. Under the previous Labor Party government, the occupied West Bank was held as a matter of security, but under Begin the West Bank is viewed as part of "the land of Israel" by historic right and must never be given up. It follows that true Palestinian self-determination there can never be permitted and that the PLO can never be represented in negotiating a deal.

There was some hope shortly after Begin's election that there were bargaining positions to be abandoned in return for concessions. But in Israel friend and foe alike say that hope is an illusion.

"When he (Begin) says never, he means never," said Yigael Yadin, the former general and archeologist who recently negotiated with Begin as head of a rival political faction.

It may be significant that Begin rejected Yadin's terms for joining the government because in Yadin's words: "He believed it was better to have a smaller majority but one which will follow him blindly rather than a bigger one which may be more trouble."

Begin's adviser on overseas opinion and long-term aide, Shmuel Katz, said of Begin's diplomatic position: "He means every word of it."

The extent to which Israelis have caught the Begin spirit is striking to a recurrent visitor. Ordiniary citizens, as well as long-term civil servants, now tell visitors that Israel has the right to decide its own positions and future without the United States or anyone else telling it what to do. The combativeness is contagious. It is as if Israel forgets it is a small country in perilous circumstances and highly dependent on outside aid.

Realizing the seriousness of his problems in Israel, Vance on arrival in Israel, said: - "I am convinced there is a growing desire of peace in the Arab countries."

At a banquet in Jerusalem, Vance delivered another gentle nudge: "We know that the process of negotiating peace, however deeply that peace may be desired, means uncertainty and change . . . After so many years of conflict, it is now easy to enision peace and it can be even harder to believe in it . . .The choices ahead lie between continuing confrontation and wars each more destructive than the past, and hold moves to reach out for peace."

There was little reaction probably or in conversation with visitors. Vance's remarks were overshadowed by Begin's combative lectures against any U.S. dealings withwhat he calls the "Nazi-like" PLO.

There is no evidence that Vance sought to apply pressure on Begin, and even less indication that such an attempt would succeed. Begin is considered unlikely to abandon positions and attitudes he has held for many years. From all indications, there was absolutely no Israeli give in discussions of the central problem revolving around the West Bank and Palestinians.

About all the United States can hope for is to keep up the appearance of live diplomacy by the talks of the United Nations next month and other such efforts. But convening a Geneva conference seems far away.

There is also the hope among some which the United States cannot express in public, that the Begin government will be short-lived. But there is no assurance of this and in the meantime conditions may deteriorate.

Sadat's rule in Egypt is given two years at the most if there are no clear moves foward peace. His replacement according to U.S. estimates, is likely to embrace rightist Moslem factions less amenable to the U.S. connection and peace with Israel.

If the drive for a settlement collapses, Israel can anticipate much more trouble in the West Bank, where military occupation will chafe all the more. Last year's election there under Israeli sponsorship produced a new crop of leaders who sent a petition to Vance during his visit aligning themselves clearly and explicitly with the PLO.

Assad is not safe in Syria if the region is in upheaval. Senior officials of his government have told diplomats that the faces will be changed - including their own - if the policy of seeking a negotiated settlement should fail. And in Jordan the crown of Hussein rests uneasily as ever.

Saudi Arabia's great interest is in regional stability. The leadership feels vulnerable atop the world's most impressive caches of riches. U.S. officials have little doubts that a sharp increase in oil prices or a cutoff of supplies - or both - would accompany a new Middle East war. Saudi Arabia is among the few countries of the world, not including Israel whose demise would be disastrous to the United States.

Israel's rejection of key elements of the U.S. sponsored bargain reaffirmed during the Vance trip means there is little chance for a comprehensive settlement. The Arabs are uninterested in lesser arrangements such as a return to step-by-step bargaining.

Because the vital interests of the United States are involved, the developing situation places the United States on a collision course with Israel regardless of the desires of White House Congress and American Jewish community. It is hard to see how, in the long run, Israel can do without a healty alliance with its chief source of aid, military and political support.

For Israel, as well as, the Arabs, the period of the Carter administration's reach for a comprehensive settlement may be seen in retrospect as the period of relative calm before the storm.