King Hussein's traditionally good relations with the influential Moslem Brotherhood movement have become strained recently over his decision to curb the spread of Islamic fundamentalism here.

Hussein timed his move to coincide with an important visit by Jordanian Prime Minister Zaid Rifai to neighboring Syria last month for reconciliation talks with Syrian President Hafez Assad, who has long accused Jordan of harboring Moslem Brotherhood opponents of his rule.

But there are strong indications that Hussein acted because he had come to the conclusion that the Moslem Brotherhood, a fundamentalist Sunni organization that already holds influential positions in several areas of Jordan's government, posed a serious threat to his own policies, especially his U.S.-backed initiative toward Middle East peace negotiations between a joint Jordanian-Palestinian delegation and Israel.

As a result, in a widely held view among government officials and western diplomats, Hussein felt the need to stem the increasingly strong tide of social and cultural fundamentalism to prevent it from turning into an organized political movement that could threaten his peace initiative.

Hussein's move, which has been described by government officials as a "warning" rather than a crackdown, has been accompanied by the departure of several fundamentalists from influential government positions and by parliamentary approval earlier this month of government-sponsored legislation aimed at preventing inflammatory preaching in mosques.

The warning came in the form of a message, widely disseminated by the state-run media, from Hussein to Rifai on the eve of Rifai's trip to Damascus to repair relations between the two countries. Rifai brought back an invitation from Assad for a meeting with Hussein, and diplomatic sources now say the two will meet in Damascus on Saturday, their first visit since 1975.

Hussein's message to Rifai accused "those who cloak themselves in our Moslem religion" of sabotaging Syrian-Jordanian relations during the past six years by aiding Syrian saboteurs working to undermine Assad's regime.

Hussein emphatically insisted that he had learned only recently that Jordan had been used as a base by subversives operating against Syria. This "minority," he said, had "deceived" him and the vast majority of Jordanians.

But, according to a Jordanian official who asked not to be identified, "It wasn't that the king wanted to appease the Syrians on the eve of Rifai's visit to Damascus as much as it was an earlier apprehension of the dangers of fundamentalism. We came to realize what rejection they the fundamentalists would form to the continuation of the peace process."

Moslem fundamentalists are outspoken in their opposition to Jordan's peace efforts.

When asked in an interview whether he was supportive of the peace process, Leith Shbeilat, a Moslem fundamentalist member of Jordan's 60-member lower house of parliament, said, "All Moslems are not, and we are not afraid of saying it, and we shall never support it."

Shbeilat said he opposes the peace process "because it is wrong." He called it "a surrendering process."

But Shbeilat said Moslem fundamentalists feel that Hussein has singled them out because he has been misinformed as to their intentions toward his rule.

There has been ample evidence, according to government officials and western diplomats, that the religious trend sweeping society was beginning to transform itself into a more organized, politicized and militant form.

Besides attacking the peace process in their Friday sermons, some Moslem imams began stressing words like "pagans" and "heretics" -- words that, in Arabic, could refer to Christians and Jews. This was particularly unsettling to Jordan's Christians, who form about 4 percent of the country's 2.5 million predominantly Sunni Moslem population.

"Some Friday sermons were outspoken" in opposition to the U.S.-sponsored peace process, one western diplomat said, "and the king was afraid of a Moslem backlash."

The government's fears were compounded by the fact that some of the fundamentalists were getting material and moral support from Libya and Iran, according to the Jordanian official.

Hussein's move also was prompted by the perception that several government departments and institutions had, over the past few years, become "infiltrated" by Moslem fundamentalists, government sources said.

"Brotherhood members had insinuated themselves into institutions where they could control the internal workings of bureaucracy," said a western diplomat.

The most dramatic example is the Education Ministry, where the main sections were headed by fundamentalists. Since Hussein's message, seven have been "retired" from the ministry, which controls the curriculums of Jordan's schools.

The Education Ministry, however, traditionally had been a fundamentalist stronghold. The realization that fundamentalists "have infiltrated certain institutions and government departments that weren't easy to infiltrate before," such as the police and intelligence departments, caused greater high-level consternation, the government official said.

Moslem fundamentalists have gained considerable ground at the country's two universities. More than half of the female students at the University of Jordan now wear the head scarf and long garments that have become associated with urban Moslem fundamentalism.

An increasing number of faculty members, many of them educated in the West, openly advocated fundamentalist ideology.

The fundamentalist trend, which was beginning to exhibit fanatic leanings despite the traditional moderation of the Moslem Brotherhood in Jordan, seemed to be fanned by the strengthening of Islamic fundamentalism in Egypt, Algeria and Lebanon.

The strength of the fundamentalists began to increase here in 1979, following the success of the Iranian revolution of Ayatollah Ruhollah Khomeini. But the Jordanian government only recently has seemed to become aware of its internal spread.

But if Hussein's move was aimed at blocking the fundamentalists from organizing into politically active entities that could threaten his moderate policies and his regime, sources say, he was not aiming to do away with the Moslem Brotherhood, which historically has served as his bulwark against communism, socialism and other leftist trends considered hostile by his government.

Hussein relied heavily on the Moslem Brotherhood in the 1950s, when leftists and Nasserites supported by Syria and Egypt were trying to overthrow him. Later, Jordan banned all political groups, and the ban remains in effect.

The Moslem Brotherhood, while not a political party, has been the only quasi-political, nongovernmental body allowed to operate in Jordan. By contrast, in neighboring Egypt, Iraq and Syria, Moslem Brotherhood members were executed, jailed and outlawed.

"The brotherhood is like the Catholic Church in Poland. It is the one legitimate or pseudo-legitimate outlet" for the people, a western diplomat observed.

One reason that Hussein has allowed fundamentalism, particularly the Moslem Brotherhood, to grow stronger, was that it proved to be a valuable tool against the influence of Syria's ruling Baath Socialist Party, which always has had a following here, causing Jordanians loyal to the throne to feel threatened.

"At one point, we made use of the Moslem Brothers to serve our own purposes, in Syria particularly," said one seasoned Jordanian political observer with official links. "Syria has Baathists in Jordan, and also, there are many friends of Syria" in this country, he said.

The presence of Syrian Baathist sympathizers in Jordan was not balanced by the presence of a Jordanian party to which Syrians could belong. Jordan, which always has felt itself to be vulnerable to the not-always-friendly political currents of larger Arab neighbors, felt threatened by this.

The Jordanian observer said that "the only way [to counter] was the Moslem Brotherhood," which, as a Sunni movement, vehemently opposed the secular, Baath Socialist regime in Syria, controlled by Moslems of the minority Alawite sect.

The brotherhood had a following among Syria's Sunni Moslem majority.

Following political violence and bloodshed in Syria -- in which several thousand people allegedly were killed, according to reports cited by Amnesty International -- an undisclosed number of Syrian Moslem Brothers received asylum in Jordan. Syria later accused Jordan of operating training camps for Moslem Brothers to infiltrate into Syria and undermine Assad's government.

The Moslem Brotherhood, formed in Egypt by Imam Hassan Banna in 1928, wants to transform society into a completely Islamic entity.

Because fundamentalists believe that Islam prescribes a comprehensive way of life that applies to the public as well as the personal realm, they do not believe in secular governments.

The brotherhood, which has a local membership of at least 300 and the support of about 10 percent of Jordan's 3 million population, believes in "persuasive change," according to Abdullah Akayleh, a Moslem Brother who represents a southern Jordanian district in parliament.

"I'd like to see Islam in politics, social life, creed, education, in every specific subsystem of our life, penetrating in every specific sector of our life," added Akayleh, who holds a doctorate in public administration from a U.S. university.

While stressing their loyalty to Hussein, both Akayleh and Shbeilat warned that if the present moderate leadership of the brotherhood loses credibility with the rank and file as the result of being muzzled by the government, some members might form more radical groups.

Although Akayleh rejected the idea that the brotherhood was being co-opted, both he and Shbeilat served on a parliamentary legal committee that worked out a compromise on a bill introduced by the government to "regulate" preaching in mosques.

The bill, unanimously passed by the lower house of parliament last week, forbids imams and mosque speakers from "incitement and making accusations against persons and institutions."

Preachers are to be appointed by the Religious Affairs Ministry, which will name a committee to supervise preaching and religious education in mosques.