Israeli Prime Minister Menachem Begin tonight flatly ruled out another month of negotiations over the removal of Palestinian guerrillas from West Beirut, while his defense minister offered to give them "temporary sanctuary" in Israel in a bid to break the impasse about where they should go.

At a large rally here in support of the government's invasion of Lebanon, Begin said that Israel already had destroyed "90 percent" of the guerrilla forces and stood ready to eliminate the remainder.

Without specifying with which American officials he had been in contact, the prime minister said he had heard this week from the United States that the negotiations on the withdrawal of the guerrillas would take another 30 days.

"I hereby declare the Palestinians in Beirut have not got 30 days," he told a cheering crowd of supporters, many of whom had come by bus from the villages and settlements along Israel's northern border with Lebanon, areas that earlier had lived under the threat of rocket attack from the guerrillas.

Begin did not say specifically how much more time he was giving U.S. special envoy Philip C. Habib to complete his negotiations before he would send Israeli forces into West Beirut. Altogether, his renewed threat to take action against the trapped guerrillas appeared more a general warning than a notice that Israel had finally taken a decision to fix its own deadline in the negotiations.

Recently, Israeli officials have said the government was not setting any time limit on the talks while at the same time indicating time was not unlimited.

Observers here said an Israeli decision to launch a ground assault on West Beirut likely would come only after a full Cabinet meeting. The next one is scheduled to take place Sunday.

Israeli Defense Minister Ariel Sharon, who spoke just before Begin, said Israel was willing to grant "immediate temporary sanctuary" to the 5,000 to 6,000 guerrillas bottled up in West Beirut.

But he laid down two conditions, saying that only guerrillas whose hands were "not covered with blood" and who agreed to quit the Palestine Liberation Organization would be welcome in Israel.

The proposal apparently was meant to break the deadlock in the talks resulting in the failure of any country to agree to take the departing guerrillas.

Sharon said he was making the offer with the guarantee that Israel would respect its word not to harm those granted sanctuary only until a solution could be found to the problem of finding a country willing to take them permanently.

Observers here doubted the proposal had much chance of being accepted anyway because of the deep suspicion or hate most Palestinian guerrillas harbor toward the Israelis, particularly after the latest bout of fighting in Lebanon.

Begin and Sharon spoke before a crowd gathered in front of city hall estimated variously at between 80,000 and 250,000 by local authorities and observers. Whatever the size, it was far larger than another held here several weeks ago by the antiwar Peace Now movement, which drew no more than 25,000.

Begin attacked the opposition Labor Party for its refusal to form a government of national unity and said in past Arab-Israeli wars a national consensus had always existed on Israel's wartime policy. He warned the opposition to the war today would not be forgotten when elections were held a year or more from now.