An arm of the Rev. Sun Myung Moon's Unification Church, a group called "Causa," or "cause" in Spanish, is pumping millions of dollars into an anti-communist organizing effort throughout the United States and in much of Central and South America.

Offering free seminars, international trips and conferences around the region to decision makers, journalists and local leaders, Causa International and its subsidiary, Causa USA, have also invested in newspapers and printing companies and in a Uruguayan bank, broadcasting station and other businesses.

The group's president is retired South Korean Col. Bo Hi Pak, chief aide to Moon, and its executive director is Warren S. Richardson, formerly chief counsel to the Liberty Lobby. President Reagan nominated Richardson to be an assistant secretary in the Department of Health and Human Services in 1981, but Richardson withdrew amid charges that the Liberty Lobby is racist and anti-Semitic.

Causa seeks to promote a philosophy called "God-ism," which Causa officials say is an alternative set of ideas for people likely to be tempted by communism. Although usually--but not always--openly financed and led by followers of Moon, Causa claims to be completely ecumenical and to have plans to put nonmembers of the Unification Church in leadership jobs.

Founded in New York in 1980, Causa has had a rocky time in Brazil, where only police intervention prevented mobs from destroying Unification churches in nine cities; and in Honduras and El Salvador, where Roman Catholic Church leaders denounced Causa as anti-Christian for its links to Moon.

But in Uruguay, Paraguay and Guatemala and in 18 other nations, Causa literature says, Causa operations are thriving despite opposition from the Catholic Church, to which the vast majority of Latin Americans belong.

Causa International has recently been most visible in Honduras, where Pak contributed $50,000 last March on behalf of Causa to a new, exclusive group of businessmen and military officers called the Association for the Promotion of Honduras (APROH).

The group is widely viewed as a vehicle for the political ambitions of its leader, Honduran military commander-in-chief Gustavo Alvarez Martinez, who is the defense minister. It started with 100 members who each pledged to give $6,000 a year, according to press reports in Honduras.

Causa had earlier given 12 Honduran notables a free trip to South Korea. They included newspaper and television editors, the presidential press secretary and a man later elected rector of the University of Honduras with APROH help, Oswaldo Ramos Soto. Causa also held a series of four-day seminars on anti- communism in San Pedro Sula, Honduras' second-largest city, for "over 1,000 national leaders," journalists and public officials, according to Causa literature.

The hotel bill alone for one of the conferences came to $70,000, one local official said.

But April 8, Honduras' Roman Catholic Conference of Bishops denounced Causa and the Unification Church, issuing a pastoral letter prohibiting priests and lay workers and "anyone who wishes to remain Catholic" from taking part or encouraging any involvement in Causa or any other Unification Church operation.

The Unification Church, the letter said, is "truly anti-Christian" and produces "a species of material and spiritual slavery."

"It is very probable that until now, Causa has not here manifested its moral and religious danger. But given its tactics, when this happens it could be too late for many," the bishops' letter said.

After that, a diplomatic source said, APROH officials told the press they had returned the $50,000 check to Pak, although Causa officials would not confirm this. A Causa effort to purchase the Tegucigalpa newspaper El Heraldo fell through. "The Catholic church was so powerful it saved us," said a leading industrialist in San Pedro Sula. "If it hadn't been for them, the Moonies would own Honduras by now."

Moon, 63, of South Korea, lives on an estate in Irvington, N.Y. He was sentenced in July, 1982, to 18 months in federal prison for conspiracy and tax fraud, but the case is being appealed.

He has been controversial since he arrived in the United States in 1971, first becoming visible politically with a 1973 publicity campaign supporting President Nixon at the height of the Watergate controversy.

Congress investigated Moon's business empire and its alleged connections to the Korean CIA in 1978 during the so-called "Koreagate" bribery scandal, describing Moon's worldwide operations as designed to further the growth of a religious cult with Moon at the center.

The Unification Church, known formally as the Holy Spirit Association for the Unification of World-Wide Christianity, claims 30,000 adherents in the United States, 3 million worldwide. Its basic theology, according to Joy Morrow, assistant to the director of the District of Columbia Unification Church, holds that God's plan to establish a divine family on Earth through Adam and Eve was foiled when Lucifer seduced Eve. All humankind is therefore born tainted.

Morrow said God's second attempt also failed when Christ was betrayed, and Moon has said he "could be" the third attempt. God-denying communism is the strongest satanic force in the world and must be defeated through educating the people, who then must take individual action, Morrow said.

But some of Moon's followers, who are often referred to as "Moonies," have left the church and charge that the cult also permits "heavenly deception" of those who have rejected Moon's message, on grounds that they are lost to Satan. They also say that Moon uses brainwashing techniques to break family ties and obtain control of followers' assets and that virtually any excess is allowed in defense of the "divine family."

Causa International, Morrow said, is "the arm of the church that's fighting communism." None of its officials would consent to be interviewed, and answers to written questions about events described in this article were not provided as promised because, an aide said, leaders "have been in a meeting for several days."

In the United States, Causa USA started out as Causa North America, bringing about 200 "friends, contacts and acquaintances of church members and [Capitol] Hill staff people" to its first three-day seminar in Jamaica last February, Causa USA director Joe A. Tully related in an interview. Conference chairman was Lynn F. Bouchey, head of the Council on Inter-American Security, a conservative think tank that has its Capitol Hill office one floor below Causa USA.

Four similar seminars have take place since: one in Reston, Va., one in Denver, and two here. Participants in each event suggested the names of people to be invited to the next, Tully said, and contacts thus made will be asked to help set up Causa offices in every state starting this month.

An advisory committee is designing plans that will take Causa's work beyond seminars and into programs that may include voter registration, journals and educational campaigns aimed at members of Congress, he continued.

Tully, 37, formerly New York director of the Unification Church, acknowledged that the five seminars had cost Causa "close to" $1 million, calling it "seed money" for nationwide expansion.

"We want to be a grass-roots organization with hundreds of thousands of people involved," he said.

Causa started in 1980 as the Confederation of Associations for the Unity of the Societies of the Americas (CAUSA), but the original emphasis on the Americas soon proved too narrow, Tully said. There was so much interest in Europe and other parts of the world that the original name was dropped and just the acronym retained, Tully said. Causa North America became Causa USA this month, and organizations eventually will be set up in every nation, he said.

"The cause is the defeat of communism, and that's not just an effort for Americans," Tully said.

The letters of invitation to past seminars identify Causa as an educational institution whose activities "are presently funded through business interests connected with the Unification Church of Rev. Moon." However, "the intent is not conversion to any given church," the letter continues, but "to provide a foundation for the cooperation of God-accepting people against the common enemy, communism."

Tully said the group "wanted to be up front" about the connection to avoid any appearance of deception. Conservatives who attended the conferences "have tended to keep at arms' length from us" but responded to the idea of an ecumenical anti-communist effort, he said.

In El Salvador, Causa officials tried to deny the Unification Church connection, according to a June 26 article in Orientacion, the official weekly of the San Salvador archdiocese. The article said Jesus Gonzalez, administrator of Causa's Honduras office, had called "to convince us that this organization and the Unification Church have no relation, in spite of having been warmed since their foundation by the same sun and illuminated by the same shining moon, the false Rev. Sun Myung Moon."

Causa had brought 155 foreign journalists and notables to El Salvador briefly in June as part of a "World Media Conference" it organized in Guatemala. Participants from 45 countries on five continents included former Vietnamese vice premier Nguyen Cao Ky and Lloyd Bucher, who commanded the USS Pueblo when North Korea captured it and held its crew hostage for 11 months in 1968.

After the group spent six days in Guatemala starting June 8, according to a June 20 article in Guatemala's Prensa Libre newspaper, Causa flew it in a Boeing 707 for day trips to Honduras, Costa Rica and El Salvador. The writers met with military and business leaders in each country, hearing from Pak and also from then-President Efrain Rios Montt of Guatemala.

Causa had begun operations in Guatemala as one of many non-Catholic sects that set up storefront missions soon after Rios Montt took power in March, 1982.

Causa apparently has had its greatest success in Uruguay. In March, 1981, Pak met in Montevideo, the capital, with top government officials, including then-President Aparicio Mendez, the vice president and the interior minister. Causa then founded a newspaper, Noticias del Uruguay, and won the right in a secret auction to build a casino and a luxury hotel, according to later newspaper accounts.

A minor scandal erupted in the Uruguayan press that summer over the award of the casino rights, which violated Uruguayan gambling laws. According to the Council on Hemispheric Affairs (COHA) newsletter of Nov. 3, 1981, the new president, Gregorio Alvarez, defended the award to Causa and said, "With respect to the fight against communism, it is obvious that we think alike."

By the end of 1981, Causa was authorized to set up an FM and medium-wave radio station in Canelones for broadcast to Montevideo and launched a second newspaper, Ultimas Noticias, in September. It also bought the largest publishing house in Uruguay, Editorial Polo; a restaurant and a meat-packing plant; and it now owns the country's biggest luxury hotel, the Victoria Plaza, according to The Latin American Newsletter of Jan. 29, 1982.

In 1982, Causa won a controlling interest of the Banco de Credito, Uruguay's third-largest national bank, and press reports said Causa had put $50 million into the bank purchase effort.

"They bought newspapers, they bought real estate, they bought generals, they bought out the country," said a Reagan administration official who was there at the time. "There was a big stink about it."

Causa and the Unification Church have been active in several other South American nations:

* Brazil: Mobs stoned and sacked Unification churches in seven cities and were blocked by police in assaults on churches in nine other towns during mid-1981. Juvenile-court judges prohibited minors from joining the sect, and the political police in Sao Paulo opened a nationwide investigation of the church. Leaders said the church had registered 5,000 members in 60 branches after one year of operation.

* Bolivia: Press reports in 1981 said Causa had applied to build a $42 million complex of office buildings, including a radio and television station, after Pak visited there in March. Later reports said the project was abandoned in the chaos of political coups.

* Chile: A seminar on "unificationism as the solution to communism" in 1981 drew high-ranking military officers and a personal representative of President Augusto Pinochet, according to the COHA newsletter of Nov. 3, 1981. It quoted Pak as saying, "I think the day will come when the world will recognize this nation as a fountain of hope" for people living under communist regimes.

* Paraguay: In 1981, Causa held a week-long seminar in Asuncion on anti-communism for members of President Alfredo Stroessner's ruling Colorado Party, following it with a series of lectures for young people in the capital. A Paraguayan publishing house, Christian Press, recently announced that it had been sold to the Unification Church. CAPTION: Picture 1, Bo Hi Pak . . . gave $50,000 to Honduran group; Picture 2, Warren S. Richardson; Picture 3, The Rev. Sun Myung Moon.