JERUSALEM -- As the antagonists of the Persian Gulf crisis look for alternatives to an all-out military conflict, the eruption of a covert war of spies, provocateurs, terrorists and assassins is an increasingly likely prospect, experts and intelligence sources say.

With the exception of propaganda battles, such a war has yet to begin.

For now, specialists here say Iraqi President Saddam Hussein is seeking to avoid potentially provocative covert action, and the United States and its allies are ill-prepared for it. Still, informed sources say, both sides are making preparations and appear more likely to act as the military and diplomatic fronts of the crisis approach a stalemate.

If it begins, the covert war will be fought on strikingly different terms than the outward conflict the world has watched during the past six weeks, specialists here say. Its setting is more likely to be the streets of Europe or the palaces of rival Arab rulers than the hot sands of Saudi Arabia; its foot soldiers are as likely to be Palestinians and Israelis as Iraqis and Americans.

Perhaps most significantly, specialists here believe that, in contrast to the military and diplomatic arenas, the advantage in covert conflict may lie with Saddam. "He is holding some strong cards that he can play," said an Israeli intelligence source. "From our side, on the other hand, the prospects are much less clear."

Both Israeli and U.S. intelligence sources have reported signs of surveillance and other preparations by Iraq and allied terrorist groups for attacks on American targets in Europe as well as in Saudi Arabia. But some Israeli specialists believe Saddam's first covert thrust might be directed against another target: the regimes of the moderate Arab states now supporting Washington, above all Saudi Arabia and Egypt.

"Right now Saddam wants to avoid any action that could provoke the United States, because the last thing he wants is a war with the West," said a senior Israeli government specialist. "But he can target the regimes of Saudi Arabia and Egypt, because by destabilizing them, he can undermine the whole Western alliance against him."

The Israeli noted that Saddam already has called publicly for the overthrow of the Saudi monarchy under King Fahd as well as Egyptian President Hosni Mubarak. "If the masses do not arise to the call," the official said, "he will probably try to help them along, by mounting his own covert action."

Using the large intelligence cadres that Iraq's General Intelligence Agency maintains in its embassies in the Arab world, Saddam could seek to foment demonstrations against the American involvement in the Gulf crisis or the "corruption" of Saudi Arabia and the gulf sheikdoms.

Iran's call Wednesday for a "holy war" against "American aggression" could assist in this campaign by helping to inspire attacks on American targets in Saudi Arabia or elsewhere.

Or, analysts said Saddam could employ a tactic that, in the Arab world, often proves as effective when it fails as when it succeeds: the assassination attempt.

In "these Arab regimes, the very attempt at assassination creates instability, and can cause popular unrest," said an intelligence source. "Most of all, it can cause fear. It can paralyze decision-making by the leaders who are targeted."

Many experts believe Saddam will not attempt broader covert attacks against Western targets unless war breaks out or the U.N. economic boycott forces his hand. If he does, they say, he is as likely to attack targets in Europe as those in the gulf -- and may use radical Palestinian groups rather than Iraqi operatives.

Nevertheless, Wednesday's call by Iranian spiritual leader Ayatollah Ali Khamenei for a holy war brought a chilling reminder of American vulernability in the Persian Gulf standoff.

Khamenei did not openly urge terrorist actions, but his vehement attack made reference to the suicide truck bomb against U.S. Marines in Lebanon. The attack was carried out by a pro-Iranian Shiite group. Khamenei said, "It's surprising how the Americans don't take lessons. They saw how vulnerable their presence can be. Have they forgotton how a bunch of pious Moslem youths . . . swept them away and evicted them from Lebanon?"

Israeli intelligence sources said, meanwhile, they have evidence that several radical Palestinian groups allied with Baghdad have been making preparations in recent weeks for possible terrorist attacks in Europe. Although they refused to spell out the evidence, the sources said the preparations typically include moving cells of operatives into place, surveying targets and trying to smuggle explosives and weapons.

A range of radical Palestinians have worked with Saddam for years, and other groups have aligned themselves with him since the crisis began. According to Israeli sources, the groups most likely to be involved in covert attacks include the Palestine Liberation Front of Mohammed Abul Abbas, which launched the May 30 speedboat attack on Israeli beaches; the Fatah Revolutionary Council of Abu Nidal, which is believed to be based in Libya, and two factions of the small May 15 organization based in Baghdad, which are led by Palestinians known as Abu Ibrahim and Abu Salen.

Although the governments of Eastern European countries no longer are willing to harbor or support such radical groups, the Israelis believe the region could now be a more handy base for terrorist operations than it was before last year's democratic revolutions. "What you have there now, in security terms, is a chaos," said a source familiar with Israel's efforts to provide protection for Soviet Jews passing through Poland, Hungary and Romania on their way to Israel. "No one is really in charge anymore, and that means that terrorist cells can operate in these countries rather easily."

To some extent, Saddam's ability to employ skilled Palestinians in a covert war is matched on the U.S. side by the Israelis, who have a long history of effective and even spectacular covert action against Iraq. In addition to the 1981 bombing raid against Iraq's nuclear reactor at Osirak -- a strike built on years of covert intelligence gathering -- Israel has carried out other operations against Iraq, ranging from its inducement of an Iraqi pilot to defect with his MiG jet in 1966 to the smuggling of thousands of Jews out of the country in the 1950s.

The Israeli secret service, Mossad, is widely believed to be responsible for the assassination of Iraqi scientists involved in weapons research. The agency's ability to penetrate the country is such that some sources say Israeli agents have been ferried in and out of the country for missions by helicopter.

For agents planning covert action today, one of the most intriguing Israeli operations against Iraq was a decade-long effort to help Kurdish rebels in northern Iraq fight the central government. Beginning in May 1966, according to informed sources, Israel secretly kept a permanent group of advisers to the Kurds inside Iraq and supplied the rebels with weapons and medical equipment, including field hospitals.

According to retired intelligence agents involved in the operation, Israeli technicians at one point built a clandestine radio station for the Kurds funded by the U.S. Central Intelligence Agency, which also backed the movement beginning in 1972. At its high point, the Israeli ex-agents estimated, the rebellion tied down up to one-third of the Iraqi army in the remote north.

The status of the Kurds in Iraq today provides an example of what official sources here say is a depleted Western ability to act covertly inside Iraq. U.S. and Israeli aid to the Kurds was suspended in 1975 when Iran, which had provided a base for the operations, decided to repair its ties with Baghdad. The rebellion subsequently was crushed, leaving the Kurds with a bitter sense that they had been betrayed by their former allies.

Fifteen years later, the Kurdish option remains "a good possibility," said Rafi Eitan, the former chief of the secret Israeli defense intelligence agency that recruited the American spy Jonathan Pollard. "But it would take time, to organize them, to get them weapons. And the Kurds will say: 'will you go on helping us this time, or will you desert us again?' They were betrayed by everyone, so now they will be less willing."

Eitan and other Israeli specialists said other covert action against Saddam's regime would face similar obstacles of infrastructure and preparation time. "To get information is easy," said Eitan in an interview. "But information is not a target in itself. To mount an operation against a target takes time and a lot of preparation. I wouldn't necessarily recommend it to the Americans."

"If there were to be a covert action against Iraq," said Ofra Banjo, a specialist on the country at the Dayan Center of Tel Aviv University, "one should have started it 10 or 15 years ago. Because to be successful, you need the support of the army or the security services -- without them, any attempt to destabilize the regime will fail."

Although Israel has a clandestine infrastructure in Iraq, the United States may hesitate to use it directly, for the same reasons it avoids the involvement of the Jewish state in its military mobilization against Iraq: fears that direct Israeli action would undermine the U.S.-Arab alliance or convert the gulf crisis into an Arab-Israeli conflict. For its part, Israel might well refuse a U.S. request to carry out a major operation, such as an attempt to assasinate Saddam.

"I would say, 'do it yourself,' " said Eitan of the prospect that Israel could be asked to kill Saddam. While stressing that he is no longer involved in such decision-making, the former spymaster added: "It's not a thing the Israeli government should take on itself."

Other Israeli specialists said that even if covert action against Iraq seemed likely to succeed, it is a weapon that would be less effective for the U.S.-led alliance than for Saddam. While Saddam wishes only to weaken the forces arrayed against him, analysts said, the United States and its allies are trying to make a political point and establish an international order, a mission for which open confrontation is more suited than quiet subterfuge.

"Even if you succeeded in assassinating Saddam, you would not solve the problem," said the Israeli government expert. "It would not necessarily reverse the Iraqi aggression in Kuwait, and it would not end Iraq's threat to the region. It would merely make Saddam a hero whose example must be followed."