The hijacking of a Kuwaiti airliner last week is part of a larger, concerted campaign by Tehran and its Arab Shiite allies to force the oil-wealthy Arab Persian Gulf states to end their support for Iraq in its war with Iran, according to western and Arab diplomatic sources here.

Virtually every Kuwaiti official and Arab and western diplomat interviewed here believes the campaign will continue unabated, and possibly will intensify, and that the ultimate Iranian objective remains the overthrow of the whole present Sunni political order in the gulf.

"They have chosen Kuwait because it is the most vulnerable and because it is aiding Iraq the most, together with Saudi Arabia," remarked one western European diplomat. "It is going to continue."

"It is the Sabah family that is in danger not just Kuwait," he added, referring to the ruling family here.

The degree to which Iran was directly involved in the hijacking will not be known until the Kuwaiti investigation is completed. Whatever the outcome, the terrorists obviously took inspiration from Iran's Islamic revolution, talked its religious language and espoused its general goals -- including the release of 17 Shiite terrorists imprisoned here.

The hijackers have not yet been tied to any one terrorist group, and sources here have pointed out the increasing difficulty of attributing a particular terrorist act to one of an increasingly bewildering array of supposed subgroups with different names and common goals.

A report in the newspaper Al Sabah, which U.S. officials have agreed with, said that "there must be some affiliation" between the hijackers and the militant Al Dawa sect, the main Tehran-based Iraqi Shiite opposition group. Investigators believe the hijackers were members of the Shiite Moslem sect and spoke with Lebanese accents. However, Al Sabah also said that the names used by the hijackers were Druze or Sunni Moslem.

There is considerable evidence already of the existence of an underground "Shiite terrorist international" stretching from Tehran to Beirut and recruiting from among the legions of dissident, or militant, Shiites in the Arab gulf states, Iraq and Lebanon.

What remains obscure is the degree of Tehran's central control and planning over the whole movement, according to Arab and western analyses of Shiite terrorism.

One theory circulating in diplomatic circles here is that both Iran and Syria, which sponsors the activities of the Iranian Revolutionary Guard in Lebanon's eastern Bekaa Valley, have lost control over this shadowy "international." This theory holds that various splinter groups have broken off from Al Dawa and begun acting on their own or in league with individual Iranian religious leaders over which the fragmented Iranian government has little or no hold.

"You are getting smaller and smaller groups of terrorists using different names," said one Arab diplomat who has long been monitoring the development of Shiite terrorism in the gulf. "The Shiites are split into small fanatic groups now." There is general agreement here that identifying the hijackers as members of Hezballah, "the Party of God," the way some Washington officials have done, does not necessarily mean much any more. In Lebanon, Hezballah is an all-embracing name, like "the Moral Majority" or "born-again Christians" in the United States, indicating a general militant religious current among Lebanese Shiites.

A faction carrying out a terrorist operation may also use it as a cover, but this is not necessarily its real name, according to western analysts here and in Beirut.

There are reports that Syria, no longer in need of the services of Shiite terrorists, has already begun trying to crack down on the Iranian Revolutionary Guards and their Lebanese allies based in Baalbek in the Bekaa Valley but is having trouble doing so.

"Once you create a monster like that, it isn't easy to keep it under control," remarked another western European diplomat.

Shiites belong to one of the main schisms in Islam dating back to the succession struggle after the death of the prophet Mohammed in 632 A.D. They regard Ali, the fourth caliph and son-in-law of the prophet who was murdered, as their main saint and a martyr, while Sunnis do not.

Iranians are almost all Shiites and have used religion and their strong ties to Arab Shiites in their campaign to export their Islamic revolution abroad.

Another theory, espoused especially by many Sunni analysts, holds that the Iranian government was directly responsible not only for choreography of the drama aboard the hijacked plane once it landed in Tehran but also for the planning and execution of the operation.

"Iran organized and financed this hijacking group," asserted one Sunni Arab ambassador here. "Iran was involved directly, definitely." This theory also holds that the Iranian leadership has decided against another big offensive in its war with Iraq for the time being and adopted instead a policy of "war by other means." Part of this new strategy would involve periodic, brief assaults on Iraqi forces to regain the last bits of occupied Iranian land and inflict as high casualties as possible. Another part would rely on the use of terrorist tactics to end the financial and other kinds of assistance the Arab gulf states, particularly Kuwait and Saudi Arabia, continue to provide Iraq.

"Now there is a serious underground Shiite movement in the Arab world, well trained in camps in Iran by specialists," the Arab ambassador said. "There is a terrorist movement carrying out activities in this area as part of Iran's policy toward the Arab world." After Saudi Arabia last June shot down two Iranian warplanes over the gulf, the Iranians are thought to be concentrating their efforts on Kuwait because it is in no position militarily to strike back and is a major financial contributor to the Iraqi war effort.

Kuwait and Saudi Arabia together give Iraq the income from the sale of 248,000 barrels of oil daily from the shared production in the "neutral zone," which straddles their common border, according to western diplomatic sources here. This amounts to about $2.5 billion annually, one quarter of Iraq's total income these days.

In addition, Kuwait and Saudi Arabia provide the most logistical support of any of the six conservative Arab gulf states, serving as transit points for arms and goods going to Iraq.

The most incriminating evidence that the hijacking may have been part of a larger Iranian-guided terrorist campaign are western press reports from Beirut that the same four names as those the hijackers used appeared on the manifest of a Middle East Airways flight to Dubai on Nov. 27.

The Kuwait airliner made a stopover on its way to Karachi, Pakistan, at Dubai airport in the United Arab Emirates, where the four terrorists boarded the flight.

Nov. 27 was the opening day of the annual summit of the six Arab leaders belonging to the Gulf Cooperation Council held in Kuwait this year. Had the hijacking occurred then, it would have caused enormous embarrassment to the Kuwaiti government, upset the summit and served as a powerful political signal to all six leaders, of Tehran's influence in the gulf.

The hijacking was far from an isolated incident of pressure on Kuwait. Since the start of the Iraqi-Iranian war four years ago, Iran has bombed an oil installation here, sent terrorists to blow up industrial sites and government buildings and hit several Kuwaiti oil tankers.

Indeed, the same day the hijackers finally were freed, warplanes almost certainly of Iranian origin attacked another Kuwaiti tanker in the lower gulf.

The Kuwaitis seem braced for this and determined to hold their ground, preferring, as the Foreign Ministry's Undersecretary of State Rashid Abdelaziz Rashid said, to put up "barriers in the street to being buried" by terrorism.

Asked by western reporters at a press conference yesterday about the possibility of more attacks, Rashid replied philosophically, "The possibility is always there. It is an international crisis you have to live with and prepare for." But, he added, "We have made our decision. We will never surrender to pressure or blackmail."

A Kuwaiti newspaper, Al Qabas, said today that the United States had flown a special combat unit to the capital of an Arab nation neighboring Iran for a commando operation to free hostages aboard the hijacked Kuwaiti jetliner at Tehran airport, The Associated Press reported.

[A Pentagon spokesman denied that any combat unit was sent.]