Although resumption of the Geneva conference in closer than ever, the decision of Prime Minister Menahem Begin to exclude any semblance of the Palestine Liberation Organization is not subject to change whatever the Arabs and President Carter say.

That determination helps explain the bunker mood here, the feeling that the Unite States and Israel may be a on collision course.

What's more, Begin is supported by politicians of almost every stripe - as of today. Outside the few Communists in the 120-member Knesset, the exceptions are a few brave, unconventional politicians who feel that "discussing" the future of the West Bank with non-PLO "notables" without the PLO present is like a wedding with no bride, only bridesmaids.

"Discussing" - not negotiating - the West Bank was a limitation agreed to in the U.S.-Israel working paper earlier this month. Israel is ready for "negotiations" leading to final peace treaties with Egypt, Syria and Jordan - but as regards the West Bank, the operative word is "discuss."

Foreign Minister Moshe Dayan put it explicitly to the Knesset: "We will discuss the issues of the West Bank [formerly Egyptian] - not a peace treaty and not the establishment of a state."

"Jimmy Carter's notion of the Palestinian issue is one that we cannot stomach," one highly informed official told us. Carter had long favored a homeland for the nearly 1.5 million Palestinian Arabs, but Israeli leaders feel they may have fuzzed that objective and blunted his flirtation with the PLO.

But in addition to Israel's determination to insulate Geneva from any taint of the PLO, Begin is pushing an Israeli formulation covering the future status of teh West Bank that defies definition. The government describes this future status as a "functional arrangement," including vague ties to Jordan but no Jordanian or any other sovereignty.

When this formulation is affixed to the ban on the highly politicized PLO, what emerges can be called a political entity by a long stretch of the imagination: murky autonomy for the Palestinians, local administration under Jordan law, possible seats in the Jordanian parliament, possible membership in the Jordanian cabinet, Israeli defense lines on the Jordan River and down the spine of the Samarian Hills.

If the PLO could be made to disappear, and if some similar (and probably unavoidable) substitute Palestinian nationalism could be magically ruled out, the plan might conceivably work. It might preserve a West Bank - Gaza Arab population as docile inhabitants in a greater Palestine dominated by Israel.

Boycotting the PLO is also seen here in a judgement that may or may not be right, as insurance for Jordan's King Hussein. Jordan's inundation by the PLO (made up to Palestinian refugees) led to a dangerous threat to Hussein's Hashemite monarchy in 1970 before his army expelled tens of thousands of Palestinians (who fled to Lebanon with tragic results).

Moreover, if the PLO virus could be killed, it might do a service for Egypt. President Anwar Sadat is perceived by Begin as a peace-seeker and thus not hostile to measures designed to smother PLO activists.

Syrian is correctly viewed here as a larger problem. Syrian concern over the growing power of the PLO propellec President Haffez Assad's army into Lebanon to cut it down, thus denying Israel a pretext - or a reason - for invading southern Lebanon.

But despite that, Syria for years had been a prime PLO sponsor. Begin's government seems so caught up in the rectitude of its plan that even Syria is given a chance - "at one minute to midnight" - of going to Geneva with only slight concessions by Israeli, if Egypt attends.

The Begin plan may be more substantial than it appears. It is designed to leave Israel with these assets: peace with Jordan, Egypt and possibly Syria (assuming there can be agreement on territorial concession); a consenus among moderate Arab states that the PLO, as a loose cannon, must be silenced; continued Israeli dominance of greater Palestine (which Begin and many other here call "Eretz Israel").

But while not ceasing to hope, realists here (and that certainly includes Menahem Begin) fear deeply - and for good reason - that the plan probably won't wash in Carter's Washinton, which explains the bunker mood. With Begin's bag about empty, that would mean very hard times ahead for Jerusalem and Washington.