Israel strategy: to take Beirut slice by slice?

The Israelis are turning their siege of west Beirut into a war of attrition - on Israeli terms.

Their two main weapons are: the intermittent pounding from land, sea, and air of the Palestinians trapped in west Beirut; and the blockade frequently denying west Beirut water, power, and food.

After a Cabinet meeting Aug. 1, an Israeli spokesman said Sunday's heavy shelling and bombing of west Beirut did not mean that the Israelis were moving into the city. Nonetheless, Israel's hold on west Beirut and the 6,000 to 9,000 hard-core members of the Palestine Liberation Organization trapped there was tightened by the capture of Beirut International Airport.

So fierce was this latest onslaught that the Lebanese government made an urgent appeal to the United Nations Security Council to intervene. In response, the council unanimously adopted a resolution Sunday demanding an immediate ceasefire and decided to send UN observers to police the new ceasefire (the ninth) announced the same afternoon.

How long these fierce Israeli tactics can continue without wrecking the efforts of United States special envoy Philip C. Habib to negotiate a diplomatic solution remains to be seen.

There are hard-liners in high places in Israel - most notably Defense Minister Ariel Sharon - who would probably not be averse to failure of the Habib mission if that restored to Israel a free hand to completely crush the PLO in Lebanon.

That was Mr. Sharon's aim when Israeli troops invaded Lebanon eight weeks ago. And, despite his insistence on ABC television Aug. 1 that ''we would like to solve it by negotiation,'' Mr. Sharon also makes it plain that he fears a negotiated outcome would allow the PLO to escape to fight another day.

So far, it has been international (and particularly US) pressure that has been largely responsible for halting the Israelis at the gates of west Beirut, where they stopped one week after entering Lebanon. Since then, diplomacy has taken over, spearheaded by Mr. Habib, who has been negotiating on a tightrope to secure the withdrawal of the PLO hard-core from Lebanon. That seems the minimum prerequisite to avoid an all-out Israeli attack putting at risk the lives of the half million civilians living in west Beirut.

Israel's aim throughout the negotiations has been to come as close as it could through diplomacy to what it had wanted to achieve by force of arms: the destruction of the power of the PLO.

The PLO, of course, has been pulling in exactly the opposite direction - with some success. The PLO's aim has been to turn initial military defeat in the first week of this fifth Arab-Israeli war into political victory.

Having survived the Israeli attack and preserved a base in west Beirut, the PLO has used the past seven weeks to increase its power and influence in and beyond the Arab world - even to the point of trying to persuade the US to reverse itself and deal directly with it.

Washington's response on this particular point is that the PLO must first unequivocally recognize Israel's right to exist before there can be direct dealings with the US.

At the end of last week, there were initiatives in two international forums intended to make it easier for the PLO to go along with Mr. Habib's efforts and leave Beirut voluntarily.

The first was by a six-man Arab League foreign ministers' committee meeting under Saudi chairmanship in Jiddah. One of the six was Farouk Khaddoumi, head of the political department of the PLO (which has membership in the Arab League). A statement from the committee July 29 said in part that ''the PLO is to announce a decision to move its armed forces from Beirut.'' Simultaneously it was made known that Syria, Jordan, Egypt, and perhaps Iraq were willing to accept PLO fighters evacuated from Lebanon.

The second initiative was in the UN Security Council. There Egypt and France introduced a resolution specifically recognizing Palestinian rights and offering a blueprint for a broad Middle East settlement. This went beyond the immediate crisis in Lebanon to include the future of the Israeli-occupied West Bank and Gaza. It is in those territories - where 1.25 million of them now live - that the Palestinians hope eventually to have a homeland of their own.

The US sees this resolution as over-ambitious and it is unacceptable to the Israelis. Debate on it was interrupted July 30 to allow the council to endorse a Spanish-sponsored resolution calling on Israel to lift its blockade of west Beirut. The next day, the Israelis turned the water back on into west Beirut but continued to bar entry of fuel (including power) and food.

Egyptian Foreign Minister Kamal Hassan Ali was in Washington at the weekend urging the Reagan administration to respond favorably to the Egyptian-French UN initiative. Presumably he also made the point that if the PLO accepted Egypt as one of the havens available as an alternative to Beirut, Egypt would be in an advantageous position to persuade the Palestinians to join the Camp David peacemaking process. Whether the PLO would be willing to reverse its previous scorn for Camp David remains to be seen.

Also flying into Washington at the weekend was Israeli Foreign Minister Yitzhak Shamir, often considered a hard-liner. The visit will enable Mr. Shamir to meet new US Secretary of State George P. Shultz. Mr. Shamir can be expected to put to Mr. Shultz without excuse Israel's arguments for both its present military tactics in the siege of Beirut and for Israel's contention that it cannot wait indefinitely for a diplomatic alternative to an all-out military showdown there.