The agreement which US Secretary of State George Shultz worked out during his 17-day Mideast trip is, of course, conditional. It calls for withdrawal of Israeli armed forces from Lebanon to take place if and when Syria also agrees to remove its forces.
If Syria does not agree to withdraw its troops, then a new situation exists in which Israel, presumably, will consolidate a more or less permanent military position in southern Lebanon.
On May 11 Mr. Shultz reported to the President at the White House and then told reporters that he was confident Syria would ultimately agree to remove its troops and thus make possible the withdrawal of Israeli troops.
Two days later, on May 13, Syria's foreign minister declared, ''We have rejected the agreement in form and substance.''
The gap between Mr. Shultz's optimism on May 11 and Syria's rejection on May 13 is explainable by the fact that Mr. Shultz is wisely and prudently attacking his problem in two parts.
It is remarkable enough that he was able to persuade the Israelis to agree, even conditionally, to remove their troops from most of the territory they spent 482 lives conquering. It was not easy to get a majority of the Israeli cabinet behind the tentative acceptance. Radical opinion in Israel favors staying in southern Lebanon.
Mr. Shultz deserves high praise indeed for having achieved that much in a mere 17 days of diplomacy.
After that it was time for Mr. Shultz to come home and take stock with the President before tackling the second part of the job, which is to bring Syria into the act. The President must now decide what the United States is willing to do to make it worth Syria's while to make peace with Israel.
Syria is heavily subsidized now by the Arab oil states, mainly by Saudi Arabia. Syria dare not agree to make peace with Israel without the assurance that its subsidy from the Saudis will either be continued or be replaced by an equal subsidy from elsewhere. It needs assurance of protection from the possibility of an Israeli attack. It needs an assured source of weapons which it is getting now largely from the Soviets.
The Syrians are fairly well off right now so long as they continue in an official state of war with Israel.
They cannot afford to enter into a formal peace with Israel unless they would be at least a little better off under a new condition.
So the real question is not whether Syria wants peace. It is whether the US can make an offer to Syria which would make peace more attractive to Syria than its present condition.
A look at the current US foreign aid budget gives a clue to what is involved.
The Reagan administration is asking Congress for a total foreign aid appropriation for the next fiscal year of $9.2 billion. Of this, $2.485 billion is for Israel and $2.075 billion is for Egypt.
Egypt was the first Arab country to make peace with Israel. It got a lot out of making peace. It got the return of all the Sinai peninsula, plus the second largest US subsidy to any foreign country. Egypt, assured of continued American generosity, has approved of the agreement Mr. Shultz worked out between Israel and Lebanon.
As yet there is no public record of what the US is currently paying Lebanon to make peace with Israel. The Shultz agreement amounts of course to a peace between Lebanon and Israel, although the formalities remain to be concluded. Nor do we yet know what assurances of future aid have been given to Lebanon to obtain its present willingness to make peace with Israel.
Add that there were private letters exchanged with Mr. Begin which are reported (this is not officially confirmed) to provide for extra American aid to Israel beyond the existing official foreign aid.
But so far nothing has been offered to Syria to make it worth Syria's while to join in the peace process.
There will have to be a ''package'' offer. It will have to include some form of US guarantee to Syria against being attacked by Israel, some pledge to resolve the Golan Heights problem, continued economic support, and continuation of Soviet arms to Syria or a Western substitute.
In diplomacy one has to take a step at a time. Mr. Shultz took a big step in bringing Israel and Lebanon into tentative agreement. Now he has to figure out with the President how much more it will cost the US to bring Syria into the peace process.