At least two Americans helped bring about the "internal" settlement signed here March 3 that is to result in black majority rule in Rhodesia by the end of the year, according to sources here.

U.S. business interests, moreover, are now joining froces with influential members of Congress in an effort to get the Carter administration to support the settlement.

One of the prime objectives of the campaigh is to remove the economic sanctions imposed on Rhodesia by the United Nations in 1966. If that is done, American companies could once again import high quality Rhodesian chrome and ferrochrome.

But the larger goal of some of these Americans is to prevent the takeover of the Salisbury government by the Marxist-leaning Patriotic Front, which would appear much less likely to give a free rein to U.S. businesses than the three African leaders based inside Rhodesia who signed the settlement.

Chief among the American legislators supporting the recent Salisbury accord are Republican Party members who are searching for issues with which to take on the Carter administration and believe Rhodesia is aparticularly good one.

At least two Americans -- one a top official of Allegheny Ludlum Industries, Inc., of Pittsburgh, the other an aggressive entrepreneur and self-made lobbyist -- were actaively involved in facilitating last week's agreement between Prime Minister Ian Smith and the three black moderates.

One of them, E. F. (Andy) Andrews, a vice president of Allegheny, is reported here to have personally intervened on behalf of Smith to help persuade Bishop Abel Muzorewa to drop his opposition to the one reamaining point holding up an agreement over constitutional safeguards for Rhodesia's 270,000 whites. The 6.8 million blacks now have practically no voice in the government.

The other, Neville Romain, has become the chief American lobbyist for Rev. Ndabaningi Sithole, leader of another African nationalist faction. Rhomain has drawn up for Sithole a "GI bill" patterned after the American model -- designed to lure Rhodesian nationalist guierrillas away from the Patriotic Front.

Romain is now en route back to Washington where he is setting up a headquarters at 1000 Connecticut Ave., from which he will conduct his lobbying activities.

Interviwed here in Salisbury shortly befor his departure, Romain was upheat about the chances of pressuring the Carter administration into backing the internal settlement. He pointed out that the growing Soviet-Cuban activities throughout Africa, including their expanding support for the Patriotic Front, were creating a favorable atmosphere.

Romain also listed half a dozen influential senators, led by Sen. Robert Dole (R-Kan), who he said were already on the side of supporters of the internal settlement.

Andrews is no stranger to the Rhodesian lobby in Washington. He played a key role in helping it get the so-called Byrd amendment, specifically allowing American companies to violate U.N. sanctions and import Rhodesian chrome, passed by Congress in 1971.

Allegheny Ludlum, together with Union Carbide and Foote Minerals were then the main American buyers or producers of Rhodesian chrome as well as the prime lobbyists for the amendment named after Sen. Harry F. Byrd (Ind, Va.). Union Carbide still has important mining interests here.

Following their successful 1971 campaigh, the Rhodesian lobbyists wrote a song celebrating the occasion in which Andrews is mentioned by name and thanke for his efforts on their behalf.

The Byrd amendment was finally repealed last year after the Carter Administration took office and energetically campaigned against it.

Andrews made a quiet visit to Salisbury Feb. 11-15, and according to some nationalist sources, he came here at ehe specific request of the Prime Minister.

Reached in Key West, Fla., where he was on a fishing holiday, Andrews denied that he had been asked to come to Rhodesia by Smith.

"Nobody asked me to come." he said. "I've been down there every February for the past five or six years."

ButJohn D. Paulus, vice president for public affairs of Allegheny Laudlum, said Andrews had not gone to Salisbury uninveited.

"It was at the invitation of the parties," Paulus said. "Either Mr. Smith asked him to go, or one of the other parties asked him."

In any event, andrews arrived in Salisbury at a crucial point in the negotiations between Smith and the nationalist leaders.

A deadlock had developed over the question of the basis for electing eight was the 23 white representatives in the proposed new, black-controlled 100-member Parliament.

During his stay in Salisbury, An- Amdrews saw three of the four leaders involved in the talks -- Sithole was away at the time -- just before they reached the compromise that cleared the way for agreement on white safe-guards to be incorporated into the new constitution.

There are conflicting accounts of just how crucial a role Andrew played in breaking that deadlock.

According to one informed nationalist source, the American told Muzorewa that his arch-rival, Joshua Nkomo, co-leader of the Patriotic Front guerrilla alliancce, was toying with the idea of returning to Salisbury to strike his own deal with Smith.

If Muzorewa did not come to an agreement, Andrews is said to have hinted, the prime minister might turn to Nkomo instead.

Andrews vehemently denies making any such effort to pressure Muzrewa. "That's just not true> that is not so, Andrews said.

Andrews said that in conversation with Muzorewa and the other leaders they discussed the issues involved in the involved in the internal settlement -- which, he added, was "the only thing in the newspapers" those days -- and that they covered all the various options.

Andrews denied playing any kind of mediator's role in the talks, "I'm not trying to be overly modest," he said. "I know all the parties and consider them good friends. But to say I went as a mediator would give me credit for something I'm not."

paulus, however, said that Andrews was "very modest" about his role.

"From what he told me" on his return from Salisbury, Palus said, "he had played an active role in talking to all parties."

he bishop's aides, fro their part, also prefer to play down Andrew's role and show some irritation over his style of diplomacy.

"He came and talke to some of us here with Bishop Muzorewa and made several sugestions as to how he thought a compromise could be reached," one of them said. "But we rejected his ideas. In fact, Muzorewa got rather angry because Andrews misrepresented his position on several things in his talks with other leaders.

The aide said the bishop dropped his demand that eight white seats be elected by voters on a common, white-black voting roll after Smith promised that the white bloe would not gang up with a black minority faction in Parliament for the purpose of forming black party. This would almost certainly be the bishop's.

Nonetheless, it is widely believed among knowledgeable black nationalist sources here that Andrews strongly influenced the bishop in his mysterious sudden change of policy between Sunday and Tuesday of the week the accord on white safeguards was finally reached.

Romain, for his part, has also been playing an important, behing-the-scenes role in boosting Sithole's political and financial fortunes as well as the black leader's image as a statesman. While Sithole was once the pauper of Rhodesia's contending black nationalist leaders, he and his organization now appear to be quite well of financially.

Whether Romain has already raised funds abroad for Sithole is not clear, but he has boasted to others that he has a number of American industrialist lined up to contribute once an agreement is in hand. He also freely admits he has helped raise money for Sithole among Salisbury businessmen.

Romain has also been instrumental in weaning a number of high-ranking members away from the bishop's party and convincing them to join Sithole's organization.

According to some Salisbury sources familiar with his acctivities, one such "defector" was Elliot Gabellah, once the bishop's right-hand man.

Romain, a South African-born inventor,self-made entrepreneur and writer turned lobbyist, has also been busy working out compromises with Sithole's lawyers during the three month long negotiations here.

One of his most important recen contributions to the Sithole negotiating team was a conference paper out-lining how the new interim multiracial government m ight go about getting Soviet and Cuban-backed guerrillas in the field to surrender their arms and return home.

The plan's objective is to guarantee all guerrillas and soldiers "the right of return to their home s and families in honor and with a secrue future wihtin the economy of the new state."

Among other things, the "boll of rights" would provide each guerrilla assistance to complete his education or other trining, and obtain formal military instrucation, jobs in the civilian sector, and loans up to $1,000 for the purchase of farms, home or businesses.

"Given proper treatment, I doubt, strongly if ether Mugabe or Nkomo would have many troops left to throw into a civil struggle once this plan is implemented," Sithole, with Romain as ghost writer, says. Robert Mugabe is the Patriotic Front's other co-leader.

The new interim government is expected to turn to the Sithole plan shortly after it is formally constitutedin its search for ways of bringing about the badly need cese-fire in the six-year-old guerilla war that has now claimed mor than 8,000 lives.

Romain prides himself on his many contacts among top Rwpublican Party officials in the United States, most notably Sen. Dole. While he says he has never been professional lobbyist before, he oozes confidence in his cause.

For the next six weeks, he intends to lobby Congress and has set his eyes upon arranging a meeting between President Carter and Rev. Sithole. He has set up appointments for Sithole in the past with Secretary of State Cyrus Vance and former Secretary of Staatte Henry Kissinger, among other high U.S. government officials and personalities.