A showdown between Arab hard-liners and Arab moderates on the issue of Egypt's peace negotiations with Israel: That is what the true leading hard-linders, Iraq and Syria, hoped to force by their surprise reconciliation last week.

But that purpose has emerged too nakedly. So Saudi Arabia, the leader of the moderates, is already moving strongly to fudge issues and avoid showdowns at the Arab summit meeting here this week.

The starting point for analysis is the Camp David summit. Its chief feature was a framework for peace first between Egypt and Israel. The logic of tha arrangement was that it militated against any resumption of serious fighting anywhere else in the Mideast.

For with Egypt committed to peace, it was hard to see how any other Arab state could take on the Israelis. The more so as Israel's other Arab neighbor with territorial claims against her, Syria, had been embroiled for years in a bitter feud with its neighbor to the east, Iraq.

The reconciliation between Syria and Iraq at first blush challenged that logic. It provides for a joint committee to work out cooperation between the forces of the two countries. Since both are supplied by Russia, and since the Syrians have over 2,000 tanks and the Iraqis over 1,000, the combination looks like a formidable fighting force.

But, in fact, Syria has only a narrow military front with Israel. A single road leads from Baghdad to Damascus, and from Damascus to the front along the Golan Heights. So the Israelis could wipe out a joint attack long before it got under way.

Moreover, the Syrians on the joint committee are known for their hostility to Iraq. On close inspection, the committee looks like a device whereby Syria can gracefully refuse forever Iraq's offer of military assitance. Militarily, in other words, the reconciliation is zero.

Far more important, however, is the symbolic act of burying the hatchet. Presidents Hafez Assad of Syria and Hassan Bakr of Iraq have sunk long-standing differences of both ideology and prestige to form a united front against the Egyptians. By that rapprochement, they delivered a message to the moderate Arabs.

The message added urgency to a previous invitation to an Arab summit meeting in Baghbad. All the hard-line states, and the Palestine Liberation Organization, had accepted that invitation. Apparently out of reasons of personal pique with Egyptian President Anwar Sadat, Jordan's King Hussein, an important moderate leader, had accepted, too. Thus it looked as though the Saudis were begin forced to declare openly where they stood on Egypt.

It was not a fun choice to have to-make. The Saudis have ambitions for Jerusalem that are not entirely satisfied in the Camp David accords. They pay subsidies to Syria and the Palestine Liberation Organization, if only to stop them from subversive activities in Saudi Arabia proper and the neighboring Persian Gulf states. But they also support Egypt financially, and the last thing the Saudis want is the unseating of Sadat by a radical regime in Cairo.

At first it was not even clear whether the Saudis would go to the Baghdad summit. But after backing and filling, they hit on a strategy. It is the strategy of attending the conference and asserting that, while some of Sadat's actions can be criticized, others are good. As the foreign minister, Prince Saud Faisal, put it: "The aim of the Arab summit" is not to isolate Egypt but to restore confidence among all Arab countries."

That masterpiece of double talk suggests what will actually emerge from the Baghdad summit - another example of divided Araby. Still, as long as the Egyptians and Israelis are in disagreement, hard-line Arabs will be on the offensive and moderates reduced to stradding. So the true lesson of Baghdad is that the Egyptians and Israelis, and their American brokers, need to get on with the peace-making.