Just 24 hours after Prime Minister Menachem Begin invited Saudi Arabian Crown Prince Fahd to Jerusalem to discuss Middle East peace, an official in the Israeli government today began questioning the sincerity of Fahd's offer to help bring the Palestinians and other Arabs into a peace agreement, under certain conditions.

Israeli Foreign Minister Yitzhak Shamir, echoing Begin's invitation to Fahd to address Israel's parliament, said Israel is prepared to negotiate with every Arab state, including Saudi Arabia, on the basis of U.N. Security Council Resolution 242 and without the imposition of preconditions.

But the Foreign Ministry's Saudi Arabia analyst, David Aphek, appeared to throw cold water on that possibility by saying Fahd's tentative offer to talk peace with Israel does not reflect a substantial change in attitude.

Fahd, in an interview Tuesday, said that statements he made to The Washington Post did not mean that Saudi Arabia was ready to initiate such action unilaterally.

Saudi Arabia "cannot take any initiative, welcome any idea or accept any decision or negotiate with any party, either directly or indirectly, except in the framework of Arab consensus," Fahd told the Moroccan News Agency in an interview also carried by the official Saudi News Agency.

[In an interview with the Beirut newspaper An Nahar, Saudi Information Minister Muhammad Abdo Yamani said Fahd's statement to The Washington Post on the issue was a reiteration of longstanding Saudi policy. "We would have liked our words to be understood a long time ago, but we are only now finding attentive ears," he said.]

Aphek, in a press conference called by the Foreign Ministry, said there were "some innovations" in Fahd's interview last week with The Washington Post, but they were designed only to improve Saudi Arabia's image abroad rather than open the door to a Middle East peace agreement with Israel.

"One interview is not enough. We shall need proof," Aphek said.

In the interview, Fahd, who continues to oppose the Camp David accords and the proposed autonomy scheme for the West Bank and Gaza Strip, pledged Saudi involvement in the peace process providing Israel formally declares its intention to leave occupied Arab territories.

Responding to that statement, Begin said in an interview with The Washington Post yesterday that Fahd would be welcome to visit Jerusalem and address the Knesset although Israel would under no circumstances withdraw to the boundaries that existed before the 1967 Six-Day Arab Israel war.

Aphek said Saudi Arabia has no interest in bringing the Palestinians of any other Arabs into peace talks with Israel, but it does have compelling reasons to "assure the survival of the Faisal family rule."

"As long as the Faisal brothers, the founding fathers, are not ripe for peace, this is a nonstarter," Aphek said. He added, "Jews are still not acceptable in Saudi Arabia."