Jerusalem — Israel stands to chalk up impressive political gains from its agreement with Lebanon - tentatively scheduled for signing on May 17 - whether or not it is ever implemented.
This fact, while touted by Israeli officials, is sometimes lost amid speculation that Syrian opposition to the pact will block its implementation, and in the face of bitter Israeli domestic political debate over whether the war - and the negotiations with Lebanon - were properly conducted.
Most obvious is dramatic improvement in Israel's relationship with the United StatEs, which had been badly strained by the lagging Lebanon talks as well as by Israeli opposition to the Reagan administration's proposal for negotiations over the occupied West Bank.
The key gain from Israel's endorsement of the accord is that if it falls through, the United States will blame Syria and the Soviet Union, rather than Israel. A boost to US-Israeli relations
The shift in US-Israeli relations has been striking and swift. No sooner had the Israeli Cabinet approved the agreement -X /o mould lead to Israeli withdrywal oJ its troops from Lebanon upon Syrian agreement to pull back its forces - than Secretary of State George Shultz hinted that the US would soon lift the suspension on delivery of 75 F-16 fighter planes held up since Israel invaded Lebanon.
US officials also began talking of issuing a much postponed invitation to Prime Minister Menachem Begin to visit the White House in June or July. And the Reagan administration yielded to a congressional increase of $100 million to the Israeli aid package.
Most gratifying to the Israelis has been the about-face of US Defense Secretary Caspar Weinberger, considered here to be the administration official most hostile to Israel. Mr. Weinberger, addressing a meeting of the American Jewish Committee in New York City on May 13, warned the Soviet Union against thinking that by obstructing the peace process in Lebanon it could ''pressure the US into a retreat from its commitment to the security of Israel.'' He added that charges that he was anti-Israel were untrue.
The conservative daily, Yediot Ahronot, which has frequently attacked the US role in the Lebanon negotiations, called the Weinberger statement of ''tremendous importance'' and ''preferable to one from the President himself.''
Another bonus: The US Defense and State departments last week freed up US technology for use in planning and joint manufacture with Israel of the Lavie fighter plane. Mr. Weinberger had opposed Secretary Shultz's decision to do this previously. The authorization of all licenses sought to date by Israel for US firms to participate in the project was interpreted here as a further goodwill move.
Israel's regional standing has also been strikingly boosted by the accord. To the south, Egypt - which withdrew its ambassador to Tel Aviv after the Sabra-Shatilla massacres of Palestinians in Beirut - will send the diplomat back after the agreement is signed, according to a report in the authoritative Cairo magazine, October.
To the north, a second Arab nation, Lebanon, will now officially leave the ranks of Arab confrontation states (even though the Lebanese themselves never took military action against Israel).
The agreement is not a peace treaty. Israel's representative in the Beirut area will have only quasi-diplomatic status and formam neg iation on movement of people and goods across the border will begin only in six months.
In the interim, the Lebanese have been cutting unofficial Israeli exports to Lebanon, down to $2 million in April from $3 million in each of the previous three months.
But the prospect of official obliteration of the state of war between Israel and Lebanon has already shaken the Arab world, especially Syria. The Syrians have labeled the agreement an extension of the Camp David process that produced the peace treaty with Egypt. Pluses and minuses
Even if the agreement is not implemented, this political clause is likely to leave a psychological residue on Israeli-Lebanese relations.
At the security level, the pluses and minuses of the treaty are less clear. This is, in part, because key security positions - including the role for Israel's ally, Lebanese militia leader Saad Haddad - remain secret.
''The nonpublished parts are critical in making this agreement work,'' said an Israeli military source, ''including our right to self-defense and all sorts of letters of understanding between Israel and the United States and between Lebanon and the United States.''
Of the plus side: A recognized 28-mile security zone will exist north of Israel's border with strict limits on weapons allowed there. There will also be a ban on organized armed forces whose aim is to attack Israel. The security zone will be policed by a special territorial brigade of the Lebanese Army. And Israel and Lebanon will man joint inspection teams with unlimited freedom of movement.