Israel today moved quickly to indicate its willingness to accept Egyptian President Anwar Sadat's call to begin preliminary talks in Cairo in preparation for a Geneva peace conference.

The unofficial reaction among many Israelis here is that if Jordan attends such a conference, and if Sadat gains Saudi Arabian approval, then Geneva can be said to have already begun.

"When the official invitation of the Egyptian foreign minister reaches Jerusalem," an official government spokesman announced here tonight," the Cabinet will decide whom to authorize to represent it at the Cairo talks."

The spokesman said Sadat's statements about total Israeli withdrawal from occupied territories and a Palestinian state were contrary to Israel's position, but he also said Israel and Egypt had agreed there would be no preconditions to a conference.

A formal reaction to Sadat's invitation is expected after the Israeli cabinet meets Sunday.

The most likely candidate to attend the Cairo talks would be Foreign Minister Moshe Dayan. A Foreign Ministry spokesman said tonight, however, that Dayan would not postpone his scheduled trip to West Germany which begins Sunday and ends Wednesday. Eight cabinet ministers gathered at Prime Minister Menahem Begin's home here tonight to hold an in- formal meeting prior to Dayan's departure.

While Syria has refused Sadat's invitation, iof Jordan attends and Saudi Arabia approves, then, in Israeli's view substantiative talks can begin. Syria would remain impotent in hits isolation - able to make neither peace nor war.

Opposition leader Shimon Peres said today that either Cairo or Jerusalem was as good as Geneva for holding the negotiations, He added that he hoped Egypt would show a spirit of compromise in its initiative.

Peres said tonight that Israel should not make Sadat's way difficult on the question of Palestinian representation nor should Israel make prior inquiries about PLO representation.

In his speech today Sadat again called for an Israeli response to his initiative in coming to Israel last week. Israeli officials, including Dayan and Defense Minister Ezer Wiezman, have been saying since Sadat left here that the time was coming fast when Israel would have to re-examine its official positions.

However, informed sources say that no reappraisal has yet taken place. Thus it is not certain when an Israeli delegation would attend a Cairo conference. It is clear, however, that Sadat means to keep up the momentum and Israel cannot afford to be absent long even if it has not fully worked out its own positions.

Although the Israelis are still working closely with the Americans, and U.S. Ambassador Samuel Lewis brought a message from President Carter to Begin tonight, many Israelis are convinced that Sadat has taken the play away from big-power diplomacy.

Israel is not altogether displeased. Israel would rather deal with the Arabs face to face - and has said so for 30 years. Moreover, Israel did not like the American concept of a Geneva conference, which calls for a settling of the main issues first and the details later.

Sadat may want the same but there is a feeling here that Israel may have more room to maneuver in its negotiations if it is free from American pressure.

Nonetheless, it is recognised both here and in Cairo that neither Egypt nor Israel can get along without the Americans now that Soviet influence has waned in Cairo. There is a recognition that Sadat was not pleased with the pace of events under the American initiative and that both Sadat and the Israelis oppose increased Soviet influence.

Former Premier Yitzhak Rabin said today that much will depend on the United States and he hlped that the Carter administration would not "miss the historic opportunity" to play its role in bringing about peace.