President Reagan said yesterday that the resumption of U.S. diplomatic efforts in Lebanon has given him "great reason for hope" that an agreement will be achieved soon for the withdrawal of Palestine Liberation Organization forces from West Beirut.

The president gave that upbeat assessment to reporters only a day after Israel's renewed bombing of Beirut caused him to telephone Prime Minister Menachem Begin to express his "outrage" and put pressure on Israel to stop the attack that had halted U.S. special envoy Philip C. Habib's negotiations.

During an unexpected visit to the White House press room, Reagan made clear that his optimism about a peaceful solution had revived in the wake of Israel's adherence to a renewed cease-fire and Habib's success in getting his talks moving again. The president said:

"I'm reasonably optimistic. Now, see, I didn't say 'cautiously' . . . . The negotiations now are not the case of trying to persuade agreement on the part of the various parties. The negotiations are on the technicalities, the logistical move that must be made in getting them out. And so, I think there's reason for, great reason for hope."

Reagan also sought to soften the impression of intense anger given by White House officials on Thursday while the Israeli attack was under way. The president said he had felt impelled to intervene personally with Begin because of his concern about new civilian casualties and because Habib's efforts "literally were broken off by the extent of that bombing and shelling. The delegates couldn't even get to the negotiation meetings . . . ."

While repeating his past contention that Israel's actions in Beirut "many times were out of proportion to the provocation," he also said that much of the criticism directed against Israel was "one-sided" because most violations of the cease-fire around Beirut resulted from the PLO attacking Israeli forces.

When a reporter noted that Israel was the invader in Lebanon, Reagan shot back: "Are they the invaders, or are the PLO the invaders? The PLO was literally a government and an armed force in another nation and beholden in no way to that other nation, which was one of the reasons why you didn't hear more protest from the Lebanese government about the Israeli presence."

He took the same tack in response to questions about whether the sharp differences between Washington and Jerusalem over how to deal with the Beirut situation have harmed U.S.-Israeli ties and affected his attitude toward the Jewish state.

Reagan said one of his reasons for calling Begin on Thursday was to point out that Israel's actions were damaging its image in this country because reports coming out of Lebanon have focused attention on Israel's severe military measures rather than the PLO breaches of the cease-fire that provoked them.

"Yes, I did and have voiced the opinion that the response many times was out of proportion to the provocation," he said. "But we can't deny that the Israelis have been taking casualties from those cease-fire violations themselves. I think the figure now is 326 dead of their own military from being attacked in the breaking of the cease-fire."

He added, in direct reference to his own attitudes: "I still believe that this country has an obligation to pursue the peace process that was started in Camp David, and that this country has an obligation to ensure Israel's survival as a nation."

Earlier, White House deputy press secretary Larry Speakes announced that Secretary of State George P. Shultz will go to the presidential retreat at Camp David, Md., today for a review of foreign policy issues, with emphasis on the Middle East.

Although the State Department has been working on studies about the best course for U.S. policy once the Lebanon crisis is resolved, administration officials said yesterday that their main emphasis remains getting the PLO to leave Beirut without further bloodshed.

Before Thursday's outbreak of fighting, some officials were hopeful that the withdrawal might begin as soon as next week; and some said yesterday they were newly encouraged that this expectation still can be met.