Prime Minister Menahem Begin today formally accepted Egypt's invitation to send representatives to Cairo for talks designed to prepare for a reconvening of the Geneva peace conference.

Begin told the Knesset that two senior aides, Eliahu Ben-Elissar, director-general of the prime minister's office, and Meir Rosenne, legal adviser to the Foreign Ministry, would head an Israeli delegation that will include technical staff, advisors, security and communications personnel.

The prime minister picked the two men, who will lead the first group of Israelis to conduct negotiations in Cairo, after consultating by telephone with Foreign Minister Moshe Dayan, who is on an official visit to West Germany.

The two officials are regarded as excellent technicians, but are not expected to play a policy making role in the talks. Observers here speculated that Ben-Elissar and Rosenne will only work out the agenda and procedure for substantive negotiations, in which Dayan himself would probably take part.

Egypt's invitation to Israel to take part in the talks was transmitted by Cairo's U.N. ambassador to Israel's U.N. envoy in what was believed in have been the first official contact between the two representatives.

The two envoys met for 40 minutes yesterday at the home of a mutual friend in New York City, and Egypt's Ahmed Esmat Abdel Mcguid handed the invitation to Israel's Chaim Herzog, his long-time adversary.

Meguid and Herzog met again today, this time at U.N. headquarters, and the Israeli envoy transmitted his government's acceptance to Egypt's ambassador.

Begin, in disclosing the U.N. contacts to the Knesset, said: "In a happy and fortunate hour, two ambassadors met, shook hands and exchanged greetings at peace." He read to the Knesset the text of the egyptian invitation signed by Dr. Boutrous Ghali, the Egyptian acting foreign secretary. It was addressed to "his excellency Mr. Moshe Dayan, foreign minister of Israel." The invitation noted that the meeting to which the parties to the middle east dispute, as well as the co-chairmen at the Geneva peace conference and the U.N. secretary gernal, were invited, is intended to prepare the conference in Geneva and insure its success. The invitation also stated that the aim of the Geneva conference is "achieving an overall settlement of the Middle East conflict in order to establish a just and durable peace."

Observers here noted that the Egyptians no longer find it necessary to use the good offices of U.S. diplomatic missions in order to communicate with Israel, but are ready now to deal directly at the United Nations, where both countries have ambassadors.

Ben-el Issar and Rosenne, who are both in their mid 40's, are experienced public servants with considerable diplomatic experience. Polish-born Benel Issar was an Israeli intelligence operative in Europe before joining Begin as his press officer just prior to last May's Knesset elections.

Rosenne is an experienced lawyer who is credited with having had a hand in the wording of the U.S.-Israel working paper on the convening of a Geneva conference that was signed last month in New York. He also took part in the Kissinger shuttle talks that culminated in the 1975 interim agreement with Egypt.

While no date has yet been set for the start of the Cairo talks, officials have thought the Israeli - delegation probably would be leaving for Cairo sometime next week. They will fly in an EL Al Airline plane, which may also carry a group of Israeli journalists who hope to cover the negotiations. A large number of journalists have registered for the flight, but Egypt has not indicated yet whether they will be permitted to make the trip to Cairo.

Begin made his announcement, accepting the Egyptian invitation at the opening of a parliamentary debate on President Sadat's visit to Israel. He repeated Israeli's call to all of its neighbors to join in the peace talks, reiterating that Israel has not offered Egypt a separate peace agreement and does not want to divide the Arab world.

Most of his speech, and particularly his summation at the close of the four-hour debate, was devoted to answering critics who argued that Israel should now declare its willingness to make substantial concessions to the Arabs.

"Let us not compete in trying to prove to each other who is more peace-loving," Begin declared. "We all want peace, and we will bring peace to our land and to our people."

Begin was short-tempered, and at times even abusive, when opposition members of the Parliament interrupted him, and he responded bitterly to demands that Israel make "gestures."

Policy is not gesticulation," he declared.

The leader of the Labor Party opposition, Shimon Peres, in his Knesset speech today called on Israel to show readiness for territorial concessions in the West Bank.

Labor Party leaders agreed in private, however, that it would have been unwise on the part of Begin to announce Israel's willingness to make compromises at this stage. The time for such concessions will come when the negotiations get into high gear, opposition leaders said.

Speculation also continued today over Foreign Minister Dayan's statement last week calling on Israeli political parties, including the ruling Likud, to rethink some of their positions on the occupied territories.

The big question pondered by observers here was whether Begin was behind Dayan's remarks, as was indicated by some of the latter's aides, or whether the prime minister is sticking to a harded line, as his remarks in the Knesset seemed to suggest today.

Israeli officials agreed, however, that the prime minister should be taken at his word when he says that Israel is not striving for a separate agreement with Egypt. They also denied that Israel hopes to continue to hold all the occupied territories splitting the Arab world and creating a stalemate. All the participants in the Knesset Debate today referred to the current period as a rare hour of opportunity that Israel must not miss.

Transport Minister Meir Amit, formerly chief of operations for the Israeli defense forces and a leader of the Democratic Movement for Change, said Israel is "entering a minefield in which there are very few safe zones."

"One needs must courage," he said, "to defuse all these mines."