Prime Minister Menachem Begin said today that he promised U.S. special envoy Philip C. Habib more time to defuse the crisis over Syrian missiles in Lebanon even though U.S. diplomatic efforts had failed so far.

Backpedaling somewhat form a warning he made on Sunday that if Habib returned form Damascus empty-handed then Israel would attack the missile batteries, Begin said he was not setting any deadline.

But, Begin said, if the diplomatic effort does not produce results, "then Israel will have to deal with this problem by her own means, and I will not mince words. We'll use military means in order to get rid of those missiles, which must not be in Lebanon."

Habib met with the prime minister for more than two hours today, after which he refused to talk with reporters, other than to say, "The diplomatic effort continues." He was expected to continue his so-far fruitless shuttle in the Middle East by flying to Riyadh Friday for more talks with Saudi leaders, who are attempting to mediate the Syrian-Israeli confrontation.

Syria deployed Soviet-made surface-to-air missiles in Lebanon's Bekaa Valley on April 29, the day after Israeli jets shot down two Syrian helicopters that the Israelis say had been supporting Syrian attacks on Israeli-supported Christian militias near Mount Sanin in the Lebanon Mountains. Israel's position is that the missiles are an impediment to Israeli Air Force operations against Palestinian guerrilla positions in Lebanon and must be withdrawn.

At an election rally in Netanya Sunday, Begin said that when Habib returned to Israel, he would ask the envoy, "Are you moving them [the missiles] or not? If you don't move them, then we will move them."

But Begin said he told Habib today, "As I said in my speech in Netanya, we don't fix any deadlines for you, and you can go on and continue with your diplomatic efforts. We wish you success in those efforts."

The prime minister said he went on to tell Habib, "But of course, your mission is to bring back the status quo ante; in other words, remove the missiles in Lebanon which Syria has put in."

At the closing ceremony of a gathering of 5,000 Jewish survivors of the Nazi Holocaust, held tonight at the Western Wall of the Second Temple, Begin vowed that no enemy would be allowed to perpetuate another holocaust.

"Israel will never allow an enemy to develop weapons of mass destruction to be used against the Jewish people," Begin said, in an obvious reference to the Iraqi nuclear plant destroyed by an Israeli attack.

Survivors of World War II Nazi death camps gathered inthe broad plaza in front of the "Wailing Wall" and lit 6,000 candles as a symbolic remembrance of the 6 million Jews who died during the Holocaust.

The prime minister told them that there were three reasons for the World War II genocide: a refusal by Jews to acknowledge anti-Semitism, international indifference to the plight of Jews and Jewish naivete.

"The Jews believed in civilization, in culture, in humanity. They asked themselves until the last moment, 'What will the world say?'"

He added, "The world will laugh at a persecuted Jew. The world respects only a fighting Jew."