In what is becoming a crescendo to the acrimonious debate over U.S. policy toward Angola, Washington is preparing to play host for two weeks to the man who stands in the center of the controversy -- a burly, bearded guerrilla chieftain of considerable charm named Jonas Malheiro Savimbi.

Heralded by President Reagan as an exemplary "freedom fighter" and embraced by conservatives as "the Che Guevara of the right," Savimbi is vilified as a "terrorist" by the Soviet and Cuban-backed Marxist government he has fought for a decade. To most of black Africa, he is a "stooge" of South Africa's white rulers.

Whatever he is, Savimbi is about to officially and publicly receive the blessings of the administration -- including the personal benediction of President Reagan and Secretary of State George P. Shultz, who will heap praise on the Angolan rebel as the leader of a grand anticommunist crusade.

Conservative groups, such as the Heritage Foundation, the American Conservative Union and the American Security Council, are orchestrating a welcome for Savimbi unlike anything Washington has ever seen for an African guerrilla leader. After his arrival Tuesday, Savimbi will use his appearances before the groups and elsewhere as a platform from which to launch his plea for military and nonmilitary assistance from the United States.

Black, Manafort, Stone and Kelly, a public relations and lobbying firm with a $600,000 contract to represent Savimbi's UNITA group, is helping to stage-manage much of the visit with a goal of exposing him to "all segments" of the U.S. foreign policy community, a spokesman for the firm said. It has arranged a whirlwind schedule of government and congressional appointments, as well as media and think tank appearances.

Savimbi is already assured a Sunday night segment on CBS' "60 Minutes," followed by appearances on ABC's "Nightline" and PBS' "MacNeil/Lehrer NewsHour," as well a possible cover story in Time magazine. He is giving the keynote speech at the Washington banquet of the American Conservative Union one night after Reagan addresses the group.

Virtually every East Coast think tank from the Carnegie Endowment for International Peace in Washington to the Council on Foreign Relations in New York has scheduled seminars, meetings or chats with Savimbi.

As an indication of Savimbi's ascent to the top of the administration's foreign policy agenda, the UNITA leader is scheduled to give the National Security Council staff a private briefing on the battlefield status of his guerrilla war; he also will make a closed-door speech to State Department officials.

The questions of whether Savimbi will receive U.S. aid and whether it will be delivered overtly or covertly remain undecided and hotly debated. The White House has submitted to the House and Senate Intelligence Committees an initial plan for $10 million to $15 million in covert military aid to be funneled to Savimbi through the Central Intelligence Agency.

Savimbi's supporters in Congress, however, want to turn the administration's proposal from a covert to an overt program, partly because they object to the CIA's surreptitious involvement in Third World conflicts and partly because they favor a larger appropriation to Savimbi than that proposed in the administration's covert plan.

Leading the pro-Savimbi campaign in the House has been Rep. Mark D. Siljander, a conservative Republican from Michigan, who has gathered 109 cosponsors for a bill that would provide Savimbi's National Union for the Total Independence of Angola (UNITA) with $27 million in open military assistance.

In the Senate, Malcolm Wallop (R-Wyo.) on Dec. 10 introduced an amendment cosponsored with 12 colleagues that would have authorized $50 million in military and other assistance to Savimbi, although the measure died for procedural reasons.

On the same day, three key Senate members tried to pass a resolution of support for Savimbi intended to lead to an aid program.

Senate Majority Leader Robert J. Dole (R-Kan.), Sen. Richard G. Lugar (R-Ind.), chairman of the Senate Foreign Relations Committee, and Sen. David F. Durenberger (R-Minn.), chairman of the Senate Select Committee on Intelligence, sponsored the measure, which favored providing "material assistance" to Savimbi early this year if the Marxist Angolan government refused to engage in "good faith negotiations" with UNITA and continued to prepare a new offensive against the guerrillas. The resolution was defeated 39 to 58.

Both supporters and opponents of aid to Savimbi seem to agree on one thing, however: a decision to support him will have repercussions on U.S. foreign policy far beyond Angola. Advocates say it will send a strong message to Moscow of U.S. resolve to "roll back" communism by aiding guerrillas fighting Soviet client states. In this context, they see the U.S. commitment as a crucial test of the so-called Reagan Doctrine.

Opponents of aid to Savimbi argue that direct U.S. involvement in his struggle will draw the United States into a damaging alliance with South Africa, now UNITA's chief backer, and make the U.S. role of a neutral mediator in the region's disputes impossible.

In November, 101 House members wrote President Reagan expressing strong opposition to renewed U.S. involvement in the Angolan conflict and urging him not to aid Savimbi. "U.S. involvement in this conflict, whether direct or indirect, covert or overt, would damage our relations with governments throughout Africa and undermine fundamental U.S. policy objectives in southern Africa," they said.

Far from promoting national reconciliation or a withdrawal of the estimated 35,000 Cuban troops stationed in Angola, the opponents argue, U.S. aid to UNITA is certain to escalate the war, increase the Soviet and Cuban commitment to the Angolan government and doom hopes for settlement of the interlocking disputes setting South Africa against its black neighbors.

Both sides also tend to agree that a decision to aid Savimbi will ring the death knell for the administration's 6-year-old policy toward southern Africa of "constructive engagement," one that has sought to rely on quiet diplomacy to nudge South Africa toward reform of its apartheid system and lessen tensions between it and black Africa.

Assistant Secretary of State Chester A. Crocker, architect of the "constructive engagement" policy, has just returned from a new round of talks with Angolan and South African officials in the search for a negotiated end to southern Africa's problems. His trip is widely regarded as the last U.S. attempt at a breakthrough before providing Savimbi with some form of aid. Crocker has given no public indication he achieved any progress.