Prime Minister Menachem Begin, reacting to reports that his planned meeting with President Reagan may be canceled or postponed if Israel escalates its military actions in Lebanon, today ordered his Cabinet to implement in his absence whatever it decides is necessary for the sake of the nation's security.

In New York for a scheduled speech on disarmament at the United Nations, Begin telephoned this afternoon the acting prime minister, Deputy Prime Minister Simcha Ehrlich, and said he had noticed "identical hints" in various media to the effect that Reagan is likely to call off a meeting scheduled for Monday in Washington if Israel "does not behave."

Cabinet Secretary Dan Merridor, who made public Begin's conversation with Ehrlich, said, "The prime minister requests that whatever the Cabinet decides for the sake of security of Israel be carried out."

Government sources said Begin appeared to be annoyed by the U.S. suggestions, adding that meetings with the president and Secretary of State Alexander M. Haig Jr. were not tentative but had been agreed by both sides.

The instructions to the Cabinet, which the prime minister is understood to have asked his staff to publicize, appeared to be a signal to the Reagan administration that critical decisions involving Israel's military options in Lebanon are beyond the influence of U.S. pressure. The message carried undertones of Begin's extraordinary dressing down last year of U.S. Ambassador Samuel W. Lewis after the United States suspended the strategic cooperation agreement with Israel. In that reproof, Begin said he would not tolerate Israel being treated as a miscreant child or a "banana republic."

The Washington Post reported Wednesday that the White House raised doubt over whether the Reagan-Begin meeting would take place, quoting administration sources as saying that Israel was being put on notice about the consequences of a possible military strike into heavily populated Beirut.

Meanwhile, a committee of two Foreign Ministry policy makers and two military experts began a series of meetings today in Tel Aviv to prepare options for a negotiated settlement on ending the Israeli Army's occupation of southern Lebanon.

Officials said the options will be presented to a special seven-member ministerial committee, appointed by the Cabinet and headed by Begin, for the drafting of Israel's conditions for withdrawing its troops from the country.

Israeli officials said that withdrawal of the invasion force depends on four basic principles, which will be refined by the ministerial committee: establishment of an internationally supervised 25-mile security zone in southern Lebanon; withdrawal of all "foreign armed elements from Lebanon, including armed members of the Palestine Liberation Organization and the approximately 25,000 Syrian troops of the Arab League-sponsored peace-keeping force there; measures to guarantee that there will be no reintroduction of the PLO military infrastructure in Lebanon; and establishment of a "free, independent and sovereign Lebanon."

A Foreign Ministry source said he saw no conflict between the demand for an internationally supervised security zone in Lebanon and the one for the country's independence and sovereignty, although the zone might be imposed against the central Lebanese government's will.

"In the Sinai peninsula , we said we would withdraw if a multinational peace-keeping force were set up, and it was. The same principle applies here," the official said. In the case of the Egyptian-Israeli peace treaty negotiations, Egypt and the United States indicated acceptance of the peace-keeping force from the early stages.

Israeli officials said Israel was not attempting to create an independent and sovereign Lebanon by diktat and according to its own interests. Instead, they said it merely wants a return to conditions on its northern border that existed before the major influx of Palestinians, which began in 1970 with Jordan's expulsion of the PLO and upset the delicate balance between Christians and Moslems in Lebanon.

Opposition Labor Party leader Shimon Peres today demanded that the Foreign Affairs and Defense Committee of the Knesset, or parliament, hold another meeting on the Lebanon crisis because he had evidence that military actions had been taken during the invasion and subsequent occupation that had not received the necessary political review and Cabinet approval. He did not specify what actions were involved.

Peres complained that while the Labor Party trusts operational reports it receives from the Army command, it has not received enough information from the Cabinet.

Labor generally has supported the invasion, but Peres' complaint illustrated an incipient debate underway in the opposition parties over the way major military decisions have been made. Some Cabinet members have complained privately that Defense Minister Ariel Sharon has obtained rubber-stamp approval of military operations on a piecemeal basis, and sometimes after the fact, instead of presenting the Cabinet with projections of military objectives.

Moshe Shahal, leader of the Labor faction in the Knesset, yesterday called for legislation that would regulate all matters pertaining to the launching and conduct of war, which, he said, is not adequately covered by existing law. Shahal said the relationship between the executive branch and the parliament was not clear enough.