The government of President Anwar Sadat, appearing confident and determined, went on the offensive today against critics of his trip to Israel.

All three Arabic language morning newspapers contained sharply worded attacks on Sadat's opponents in the Arab world. These editorials contributed to an atmosphere of excitement and anticipation that the government has done little to dispel, as the belief mounted that Sadat would announce in a speech scheduled for Saturday some major agreement with Israel on the question of Palestinian representation at Geneva.

Egypt also closed down two Palestinian offices here and expelled the head of the Palestine Liberation Organization diplomatic mission, Jamal Sourani, who held the rank of ambassador. Police said about 15 Palestinians had been expelled in the past few days for denouncing Sadat in leaflets and statements.

A few warnings that the gap between Israel's terms for peace and those Egypt remain wide and that long, difficult negotiations have only begun, have failed to dampen the optimism generated by the extensive publicity.

Sadat met this morning with U.S. Ambassador Hermann Eilts in an apparent resumption of U.S.-mediated indirect negotiations between Egypt and Israel.

The acting foreign minister, Dr. Boutros Boutros-Ghali, began calling in the ambassadors of foreign countries to explain the reasons for the trip to Israel and to ask for their support.

He began this morning with the African nations, most of which broke diplomatic relations with Israel after the 1973 Middle East war.Cairo radio said Boustro-Ghali urged them not to be in a hurry to resume those relations, saying they should wait until a peace agreement has been reached!

Tonight it was the turn of the ambassadors from the other Arab states, some of which have been violently critical of Sadat. Boutros-Ghali told reporters at the scene that he informed the ambassadors that Egypt's terms for peace have not changed - full Israeli withdrawal from the territories occupied in 1967 and recognition of the rights of the Palestinian people. He said Sadat's trip was necessary to "break the stalemate" that had developed over Middle East peace negotiations.

Arab journalists at the Foreign Ministry said the ambassadors of Libya and Syria did not attend. Both have been furiously opposed to Sadat's mission to Israel and have been working to arouse Arab sentiment against it.

Far from bending before the outcry from its Arab critics, diplomatic analysts said, Egypt now appears determined to press ahead with its spectacular peace initiative, so much so that there is speculation here that Egypt would go to Geneva even without Syria and the Palestine Liberation Organization, as it did after the 1973 war.

Some experienced observers believe that in the Egyptian view, such a Geneva conference would be an extension of the previous one, in which Egypt and Jordan participated but Syria did not and the PLO was not invited. Egypt would go not to make a separate deal for itself but to press the claims of Syria and the Palestinians as well.

The editorials in the Cairo press this morning appear to have accurately reflected the Sadat government's response to the critics in Syria, Libra, Iraq, Algeria and the PLO. Government officials have been saying privately the same kinds of things that were in the papers this morning.

Al Akhbar, which has the largest circulation, berated those who "are so enthusiastic for war but expect Egypt to wage it."

In Al Combouria, an editorial referred to the triumphant return home by Sadat and said, "The people said yes to security and peace, no to those who deal in polemics, illusions and dreams."

The most influential paper, Al Ahram, denounced "those who live in the past, governed by its complexes and dogmas, under the illusion that the way to Jerusalem is through the radio waves and melodramatic statements." The paper said that without Egypt there can be no peace, without Egypt there can be no Arabism."

This has been the essence of Egypt's challenge to the Syrians, to the PLO and to the Arab rejectionists - in effect, saying to them: show us what your way has accomplished for the Arab cause and what your way was going to achieve and we will defer to you, but if you cannot show us that, we are the ones who will choose the way because it is Egypt that bears the burden of war.

In the face of Sadat's determination, the hard-liners appear to be making little if any headway in their anti-Egyptian campaign.

After a Cabinet meeting this mornign in Kuwait, which, with its vast wealth and heavily Palestinian population, carries a lot of weight in Arab affairs, the government issued a statement reaffirming its commitment to the conditions for peace adopted by previous Arab summit conferences and regretting "serious disagreements at this critical period" among the Arabs.

The statement omitted any direct criticism of the Sadat trip to Israel, and its peace terms were exactly those Sadat himself has been telling the Israelis they will have to meet.

Foreign Minister officials and other informed Egyptians expressed confidence today that Sadat would be able to announce on Saturday some important Israeli gesture to the Palestinians that would allow him to claim success for his trip.

One of the many oddities of this momentous week in Egyptian history, however, is that the sources of real information about what is going on - never very forthcoming even in the best of times - have all but dried up. This is not because the government is keeping any secrets, but because the country has been observing the year's biggest religious holiday.

Some key Foreign Ministry officials have been at the seashore. The press office of the presidency has been closed most of the week. The English language newspaper skipped two days of publication. The Information Ministry has been working only to issue press credentials for newly arrived journalists, not to arrange any appointments. The Foreign Ministry is in disarray since its leader, Ismail Fahmy, resigned last week and other top officials were transferred.

Thus, there may be less than meets the eye to the optimism about possible Israeli concessions.

Boutros-Ghali, in an interview on French television, warned that "the Middle East crisis cannot be resolved in a day or a month . . . There will have to be lots of negotiations."

He said it would be six months before it became clear whether Sadat's venture would bear fruit or not after his meeting with the Arab ambassadors tonight, he said that no date has been selected for the Geneva conference, and that Egypt was determined to adhere to its demand for a comprehensive settlement that could be accepted by all the Arab states in the conflict with Israel.