Egyptian President Anwar Sadat won endorsements today from Jordan and Sudan for his bold mission to Israel, lessening somewhat concerns that his trip had left him isolated in the Arab world.

Anger over the trip remained intense, however, in hard-line Arab quarters, and a Syrian tirade accusing Sadat of "surrendering to the Zionist butchers" provoked an Egyptian walk-out from the U.N. General Assembly.

In Damascus, Syria and the Palestine Liberation Organization issued a joint statement that, in effect, called for a coup against Sadat, urging the "Egyptian people and army to confront this national treason."

Many Arab leaders continued to withold judgment on the Egyptian president's journey, but Sadat could not fail to have been heartened today by a first, tentative sign of support from Jordan, which appeared to be wavering throughout the history-making weekend.

Jordanian Information Minister Adnan Abu Odeh told reporters in Amman that "this visit has broken the ice and removed the psychological barriers and brought fresh hope" for a new Geneva peace conference.

Odeh's statement does not carry the weight of a personal endorsement by King Hussein -- who still has not committed himself on Sadat's trip -- but it was an encouraging reversal from the sharp criticism of the Egyptian leader that had been appearing in Jordanian newspapers.

Sadat also picked up strong backing today from the President of Sudan, Jaafar Nimeri, who came here for a five-hour visit and proclaimed the Egyptian president's trip a "big victory" for the Arabs.

Cairo Radio quoted Sadat as saying after their meeting that Sudan had "projected my rear" while he was in Israel. The Egyptian leader also reportedly told Nimeri that his message to the Israelis had instilled in them "a respect for our will, the will of the Arabs."

Sudan thus joined Morocco and the sultanate of Oman, two monarchies on the geographical and political fringes of the Arab world, in publicly supporting Sadat.

Sudanese support had been expected, since Sudan is perhaps Egypt's staunchest ally and Nimeri is close to Sadat personally. More important was the first declaration of approval from Jordan, which is one of the so-called confrontation states.

Jordonian Prime Minister Mudar Badran meanwhile, made a surprise visit to the Syrian capital of Damascus.

Jordan and Syria, once bitter enemies, have developed close ties over the past year and are embarked on a program of economic and political integration.

It would mark a tremendous victory for Sadat -- and greatly simplify the task of bringing the Arabs to Geneva -- if Jordan could persuade Syrian President Hafez Assad to at least moderate his bitter opposition to the Egyptian leader's move and allow his diplomacy to run its course before deciding whether to break with Sadat completely.

Other Arab leaders, however, are pulling Assad the other way.

The fiery joint communique today appealing for opposition to Sadat followed a meeting between Assad and PLO leader Yasser Arafat.

It also called for "progressive" Arab parties to unite with Syria and the PLO to "face the Sadat-Zionist-imperialist conspiracy."

Abdel Salam Jalloud, the No. 2 man in the government of Libya, has been visiting Syria and Iraq in an appararent effort to patch up relations between the two countries.

Syria and Iraq have been feuding for years over the ideological directions taken by their rival wings of the Baath Socialist Party. That split is so deep that observers here believe it unlikely that the Syrians would make common cause with Iraq against the Egyptians.

While Syria and Iraq might share the same view of Sadat's personal diplomacy, they are enemies of such long standing that they can hardly be expected to work in partnership.

Some analysts believe that Syria does not in fact have much much choice but to tolerate, however grudgingly, Egypt's diplomatic initiatives. With much of Syria's army tied down in Lebanon, its border with Iraq closed and its partner Jordan wavering, it may be Damascus rather than Cairo, that finds itself isolated.

As a diplomat in Damascus put it when the visit was announced, Syria is dealing from a position of weakness and risks seeing other Arabs states conclude a peace agreement while getting nothing for itself if it refuses to go along with the Egyptian maneuvers.

Syria has long feared that Egypt would conclude a separate peace agreement with Israel, and even though Sadat pledged in his Knesset speech not to do that, his trip still exacerbated those fears.

The newspaper Misr, organ of the dominant political party in Egypt, reported today that Sadat told reporters on his Homebound plane that Israel had offered a separate deal -- all of the Sinai peninsula in exchange for peace -- but Sadat turned it down.

True or not, the story has the effect of re-lating Egypt's promise to deal on behalf of all the Arabs, not just for itself.