Foreign Minister Moshe Dayan said tonight that he does not foresee any substantive negotiations during Egyptian President Anwar Sadat's expected visit to Israel. Nevertheless, if Egypt indicates it is willing to discuss a separate peace treaty, Dayan said, Israeli is ready.

Dayan spoke on Israeli radio as the country, still stunned by the startling developments of the past week, awaited an official response from Sadat to yesterday's formal invitation to the Egyptian leader to visit Jerusalem.

Israeli officials said they expected Sadat to delay his reply until he returns to Egypt following his current trip to Syria and perhaps other Arab countries. He was believed to be briefing Arab leaders on his plans.

But not a day seems to pass without a surprising new "first" in relations between Israel and Egypt, and today was no exception.

When 600 Israeli and foreign leftists gathered in Tel Aviv today for a symposium, they were read a cable of greetings from Sadat.

The message, routed from Egypt to Israel via Cyprus, marked the first time that an Arab leader had ever sent a note of welcome to an event in the Jewish state. It was greeted with loud applause.

Dayan, meanwhile, in his radio interview, said that if there were a "shadow of hope, the slightest crack" that Sadat might be willing to negotiate a seperate peace treaty on his forthcoming visit to Jerusalem, Israel would take advantage of the visit to seek one.

But, Dayan said, Sadat has made it clear that he would not sign a separate agreement. If Israel asked him to do so, knowing in advance he would refuse, Dayan said, it would be "interpreted as a hostile step toward him and others."

The possibility of a separate deal between Israel and Egypt has always frightened the Syrians and the Palestinians - and with good reasons.

"Egypt is not just one of 22 Arab states," former Foreign Minister Abba Eban observed the other day. "It has half the population of the Arab world. It is acknowledged center of Arab politics and culture."

A separate peace between Israel and Egypt would leave very little leverage to the Syrians and the Palestinians, let alone the Jordanians. That is why Syria was so opposed to the Sinai agreements of two years ago.

Of all the Arab leaders, Sadat is the most committed to obtaining a peace treaty because his political prestige - some say his very political survival - is at stake.

Egypt's economy is in a shambles and Sadat badly needs a peace that does not damage his country's prestige. Despite his need, however, Israeli planners do not think that Sadat can be separated from the general Arab cause - at least for the time being.

Israel would find it easy to make a separate peace with Egypt, not only because the Israelis know that Egypt badly needs a settlement, but also because of geography.

It is simply safer to Israel to make territorial concessions in the Sinai desert, 125 miles away from the country's population centers.

The occupied Golan heights of Syria overlook the farming communities of the Galilee. As for the occupied West Bank of the Jordan, it is only seven miles from the seat at Israel's narrowest point.

While Israel awaits a reply from Sadat, Prime Minister Menahem Begin moved ahead today with plans to be in Britian early next week. Altough several dates have been put forward for Sadat's visit to Jerusalem, the two dates most talked about now are Thursday, Nov. 24, and Monday, Nov. 28. These are considered the earliest dates that Sadat might come.

If Sadat does visit Jerusalem - and it is now taken for granted here that he will - he will set a new precedent in addressing Israel's Knesset (Parliament). Only three foreigners have ever been allowed to speak from the podium: the president of Malawi in 1968, the president of the U.N. General Assembly in 1970, and the president of Costa Rica last year.

On these occasions, however, only official "greetings" were involved. Sadat would be the first foreigner to address the Knesset on any subject he wishes.

As Sadat has expressed his desire to talk with all the Knesset factions, a visit of more than one day is anticipated. Very little has been done, however, in the way of preparations.

According to the Jerusalem Post, flag manufacturer Yitzhak Berman has already started producing Egyptian flags without waiting for an order from the government. "If he comes and the ministry orders them, then find and good." Berman was quoted as saying. "Ifo not, nothing will be lost because they will be snapped up by collectors.

Israeli television also reported tonight that the official red carpet at Ben Gurion Airport had been sent to the cleaners.

No one knows yet where Sadat and his party would stay in Jerusalem. The King David, where former President Nixon and Henry Kissinger stayed, is the city's best known hotel. In British times, it was run by the same management that ran famous Shepheard's Hotel in Cairo - the finest watering spot in the Middle East until it was burned to the ground by an angry mob in the early 1950s.

In another development today, Defense Minister Ezer Weizman was injured, but not seriously, when his car turned over in a traffic accident. He had just left a meeting with Israel's chief of staff. Gen. Mordechai Gur, whose published view that Egypt might be planning a war with israel provoked Weizman's deep displeasure.