Two weeks ago, an assassin pumped three bullets into Ziad Sati, a senior Jordanian diplomat driving to work in Ankara, Turkey.

"That was a signal," a senior Jordanian official said a few days afterward. It was a Syrian response, he suggested, to calls for an Arab summit conference that might seriously criticize and isolate Damascus.

Despite Syria's refusal to attend, that Arab League summit meeting is to begin here Wednesday, with at least 16 countries and the Palestine Liberation Organization taking part. Foreign ministers began arriving yesterday to make preparations.

No proof has been presented publicly to link Syria directly to the July 24 murder. But in Arab politics much is left unsaid and context often is taken to be everything.

"The Syrians will stay away," the Jordanian official said. "But they are going to be betting on scaring others into staying away as well."

As an example of the growing threat seen from Syria, some Arab officials cite a comment Saturday in Syria's government daily Tishrin that "Syria will not deal with the summit nor with its results. . . . Syria and the Arab masses will know how to punish traitors."

Yet the summit appears certain to be held here on Wednesday. At least 17 of the Arab League's 22 members are expected to attend, many of them making the point that they were ignoring or defying threats by Damascus.

Foreign ministers or delegations from 10 countries, including even Syria's ally Libya, have arrived for preliminary talks today.

Members of Yasser Arafat's PLO, which attends as a national delegation, talk bluntly of the summit as a showdown with Syrian President Hafez Assad. They have pushed for it as a way to denounce the Syrian-backed war on Palestinian camps in Lebanon that cost a reported 800 lives in June and July and could erupt again soon.

The summit is "a challenge to the Syrian will," said Khalil Wazir, a top PLO official interviewed in Jordan.

Yet the initial call to meet here by the head of the Arab League, Moroccan King Hassan II, appeared to have failed late last month when the Saudis and the Persian Gulf states privately expressed reluctance to come.

Publicly they talked about the need to preserve Arab unity, an impossibility if Syria refused to attend. But western diplomats and other Arab officials suggest that they were also intimidated.

When the Syrians began to say in their press that they had stopped the summit, however, some Arab leaders appear to have felt they went too far.

One Arab official active in backstage efforts to keep the summit alive said Hassan was angered by Syrian press reports suggesting that even Morocco was not beyond the reach of Syria's intimidation.

At the same time, Jordan's King Hussein called for a new "constructive alliance" among Arab nations, openly suggesting, in effect, that it was better for the Arabs to break ranks and live by majority rule than to do nothing while hoping for unanimity -- especially on the delicate matter of the peace process.

Only two days after it appeared that the summit was to be postponed indefinitely, Hassan announced that it would be held here on Aug. 7.

"This idea and this spirit that Syria was moving with was seen by many Arabs as an effort to blackmail them," Wazir asserted. They are "fed up with this kind of blackmailing."

Saudi Arabia made the key decision last week to attend, although it was reported today that King Fahd probably will not come. The rest of the gulf states followed the Saudi lead, many of them declaring in general terms that they would not be intimidated by terrorism.

"They want to show they are not afraid," a well-informed Arab gulf journalist said. "But they are."

The summit conference could make major decisions that contradict Syria's foreign policy. It is likely to back Iraq in its war with Iran, while Syria is allied with Iran. The summit also may endorse the peace process embarked on by Hussein and Arafat -- a major point on the preliminary agenda.

The State Department called the summit "a significant event" and said the United States hopes the Arab leaders will reinforce Hussein's initative.

The summit meeting also could bring Egypt officially back into the Arab fold, although that item is not yet on the agenda. Egypt was isolated by the Arab world after signing the Camp David accords with Israel.

Jordan renewed diplomatic relations with Cairo last year and Iraq has close ties that fall just short of official recognition.

Egyptian President Hosni Mubarak last week called on the Arabs to "free themselves from intimidation and terrorism practiced by some Arab countries against them."

Any of these moves is likely to lessen Syrian prestige and influence.

There have been no renewed attacks on the moderate Arab states since the summit was rescheduled. But in the past there has rarely been much warning before violence struck -- only context. And in the context of the issues to be brought up at this summit, the usual target has been Jordan.

At the end of 1983, as Arafat and his PLO were renewing their ties to Jordan after brutal fighting with Syria, there were four attacks on Jordanian diplomats and embassy employes abroad.

At the end of 1984, after the PLO's Palestinian National Council met in Jordan in defiance of Syria's expressed wishes, a Jordanian diplomat in Bucharest was killed and one in Athens narrowly escaped assassination.

A moderate Palestinian leader, Fahd Kawasmeh, newly elected to the PLO executive committee, was murdered last December.

After Hussein and Arafat announced their joint peace initiative in February, Jordan's national airline, Alia, became a target.

In March its office in Cyprus was bombed. In April the building housing the Jordanian Embassy in Rome was hit by a rocket, a rocket hit the tail of an Alia passenger plane in Athens, and an Alia plane was hijacked to Beirut and blown up.