The Reagan administration, struggling to restore the shattered cease-fire in Beirut, wants Israel to refrain from further attacks on the besieged city for roughly two weeks to provide time for a final test of whether the withdrawal of Palestinian fighters can be accomplished through negotiation rather than bloodshed.

In addition, as a means of giving the negotiations renewed credibility to the Palestine Liberation Organization, the administration revealed yesterday that it is asking Israel to surrender the military advances it has made in West Beirut this week and return to the positions held by Israeli forces last Sunday. In a statement yesterday, the Israeli Cabinet made no specific reference to Reagan's appeal, but made clear Israel's intention to hold to its current position until the Palestinian guerrillas leave Beirut.

Although the heavy fighting inside Beirut has subsided into sporadic exchanges, U.S. officials said that, as of last night, they still had not received any direct answer from Israeli Prime Minister Menachem Begin to the appeal for restraint made by President Reagan in a private message to Begin on Wednesday.

Administration sources said yesterday that a breathing space of roughly two weeks is necessary for Reagan's special envoy, Philip C. Habib, to determine whether the PLO really intends to go through with its promise to leave Lebanon and, if so, to work out the details of the evacuation of PLO guerrillas to other Arab countries.

According to these sources, Reagan's determination to give the Habib mission every possible chance for success underlies the heavy pressure being exerted on Begin to refrain for the necessary time from new military moves like this week's massive assault against West Beirut.

In his letter to Begin, Reagan is known to have given an implicit warning that further attacks could force him to consider a suspension of U.S. arms supplies to Israel.

A delegation of American Jewish leaders who met with top administration officials yesterday said afterward they had been told the president is not now considering sanctions. This statement was made by Julius Berman, chairman of an umbrella organization of U.S. Jewish groups, following the meetings with Vice President Bush, Secretary of State George P. Shultz and Defense Secretary Caspar W. Weinberger.

But, in an interview later, Berman specified that his remark about sanctions applied only to his understanding of the situation at the time of the meetings yesterday morning. "I can't say that they told me it wouldn't be something different tomorrow or the day after," Berman said.

Administration sources, while acknowledging that Reagan does not want to do anything that might seriously affect U.S.-Israeli relations, also stressed that there is what one called "intense frustration" here over Israeli actions that interfere with Habib's efforts.

While conceding that no decisions have been made, they insisted that all options, including a possible resort to sanctions, would be considered if continued Israeli recalcitrance makes it impossible for Habib to continue.

According to these sources, the administration's yardstick in deciding what to do next will depend not on the rhetoric that comes out of Jerusalem but on the actual moves that the Israelis make and their effect on the Habib mission. As one source put it, "We probably won't make an issue about Begin talking tough as long as he doesn't follow up the talk with actions that keep bringing the negotiations with the PLO to a halt."

Although Habib's efforts to work out a diplomatic settlement have been going on for almost seven weeks, the sources said he has been hampered severely by breaches of the cease-fire every two or three days. They noted that each outbreak of fighting brings the talks to a halt and creates new tensions that are increasingly difficult to overcome.

As a result, the sources continued, there has not yet been an opportunity to get an accurate gauge of whether the PLO is sincere about carrying out its professed intention of having its leaders and guerrilla fighters leave Beirut and then Lebanon.

The sources asserted that this sincerity can be tested only if Habib is given sufficient time to work out all the complex details of a plan to evacuate the PLO.

They estimated that this will require a time frame of roughly two weeks; and, they added, over the course of that period, it would be possible, at a minimum, to determine whether the PLO is serious or simply stalling and, at a maximum, to actually get them out of Lebanon without a resort to an all-out Israeli military assault.

The sources conceded that there are differing assessments within the administration about the prospects for Habib achieving this maximum objective.

But they added that Habib believes he has a reasonably good chance of succeeding and that Reagan, who has been kept closely informed of his views by the State Department and national security affairs adviser William P. Clark, is determined to back Habib as long as the negotiator believes that it is worth continuing.

Although there has been a growing impression that Habib hasn't made much headway, the sources insisted that his efforts so far have produced greater results than are apparent.

In particular, they said, substantial progress has been made in reaching agreements for other Arab countries to take the PLO evacuees, whose numbers may reach as high as 6,000.

According to the sources, the largest number is expected to go to Syria, with others being resettled in Iraq, Jordan and various smaller Arab states. The sources added that there is still a chance that Egypt, which has been refusing to accept any unless the evacuation from Lebanon is tied to U.S. recognition of the PLO, will be induced to change its position.

The sources said the U.S. call for Israel to give up its gains of this week and return to the positions that existed last Sunday was intended to reassure PLO leaders about the credibility and good faith of the negotiations.

In the past, they noted, there have been strong suspicions about the believability of U.S. evenhandedness because almost every disruption of the cease-fire has resulted in Israeli advances that tighten the pressure on the PLO's positions.

The sources acknowledged that they did not know whether Begin could be induced to make such a concession. They added that, while his refusal clearly would be unhelpful to the U.S. strategy, it still is too early to tell what impact it would have on the negotiations.

Although the administration's policy is to refrain from public comment about the details or progress of Habib's mission, one upbeat assessment was provided by Weinberger. Asked by reporters if he thought the PLO can be removed without further use of military force against it, he said:

"I think that can be done. We have made measurable progress toward that. I think he Habib can succeed."

Bush, talking with reporters after the meeting with the Jewish leaders, reiterated the point, made by Reagan on Wednesday, that the United States still shares Israel's view that the PLO should leave Lebanon. But the vice president also underscored that the United States strongly disagrees with the tactics used by Israel in pursuit of that goal.

"The PLO must withdraw; they must withdraw promptly . . . and this should happen with no more loss of innocent human life in Lebanon," he said.

Saudi Arabia's King Fahd, one of America's closest allies in the Arab world, called the White House for the second straight day yesterday to express his concern about the Lebanese crisis. White House deputy press secretary Larry Speakes, in confirming the call, said only that it had been taken by a senior official.

However, the Saudi press agency reported from Jeddah that Fahd called on the United States to "take speedy action to stop the escalation in Beirut," and charged that this week's fighting "exposes Israel's premeditated intention to dynamite peace efforts."