Less than two years after the Argentine military seized power from President Isabel Peron, a serious split appears to be developing within the ruling junta.

The head of the Argentine Navy, Adm. Emilio Massera, is increasingly expressing openly his disillusionment with the leadership of President Jorge Rafael Videla, the head of the Army.

Massera, according to a well-informed source here, would like to visit the United States to tell President Carter that unlike Videla, he is dedicated to halting human rights violations in Argentina and paving the way for an early return to democracy.

The actions of Massera would appear to carry with them a considerable risk, since the Argentine Navy is a far smaller and less formidable force than the army, traditional rival.

Nevertheless, at least some top Navy officers appear to feel that a realignment of the government that would include tha naming of a new president might be possible if the United States withdrew its support of Videla.

"If the United States didn't support Videla, he would fall," a source sympathetic with navy aims said.

"Sources close to Massera deny he is looking to increase his own power.

Argentine human rights activitists further say they have been little evidence that Massera, 52, who has served and supported a number of different governments including the Peronists, is any more sympathetic to their cause than Videla.

He's without a doubt the most intelligent" of the junta members, one rights spokesman said of Massera, "he has no moral principles, but he's a pragmatist. There is a possibility he would be better, but the probability is not very high."

But in a series of informal meetings with U.S. officials and interested civilians in Washington and New York last month, two Argentine Navy captains tried to explain how they and their chief, Massera, were eager to improve Argentina's international image.

The Navy, they said on several occassions, wants to publish the complete list of political prisones held by the junta. These secretly held prisoners, believed to number in the thousands, are the principal black mark on Argentina's severely tarnished reputation.

The navy, they said, also wants to transfer all the prisoners held in military camps and subject to secret military trials, over to the civilian courts. It wants a plan for an early return to democracy. It wants better relations with the United States.

The reason the Navy cannot have these things the captains - and other Navy officials here - said, is because Videla and the army won't permit it.

In subtle ways, like the meetings with Americans, and not-so-subtle speeches here, Massera is trying to convince the Western world and the Argentine people that they have misplaced their eggs in Videla's basket.

The growing schism within the Argentine junta, pitting Massera and air force Gen. Orlando Agosti against Videla, is the first visible crack in the military monolith that seized power here in March 1976.

A junta, as the Spanish word implies, is a sort of board of directors. But while the board of a private company is ideally made up of members with differing opinions, a military junta, at least to outside eyes, ideally has no differences of opinion.

The problem with maintaining the ideal of a united front, however, is that there is no one to blame when things go wrong. As Argentina's international critics have looked for culprits in the deteriorating human rights situation, blame has usually fallen on the navy as the "hard-line" faction within the government.

Not only is that blame misplaced, the navy now says, but the navy's bad image, and the bad image of Argentina as a whole, comes from ineptitude and plotting by its traditional and much larger rival, the army.

To counter the navy's bad image, Massera has made a symbolic break with the junta, in speeches like his call last month for an end to "lamentations" and "frustrating inaction."

In October, Massera, a handsome career officer, toured Europe, where he assured government leaders that Argentina was on the road to recovery. Currently, his aim is a trip to the United States, perhaps under the guise of a military exchange mission with a high-ranking U.S. Navy officer, to tell President Carter face-to-face that he is for democracy.

One source who is both well-informed and sympathetic with navy aims, said President Videla remains in power because "the United States supports him."

Examples of that support, he said, were Carter's warm welcome of Videla during a September visit to Washington and Secretary of State Cyrus Vance's trip here in November.

While the Carter administration has cut off military assistance to the junta on human rights grounds, U.S. officials generally view Videla as a military moderate and Argentina's best hope for stopping human rights abuses by military subordinates and reestablishing a democratic system. While incidents of leftist terrorism have virtually stopped during the two years of junta rule, disappearances and allegations of torture and murder by the government and rightist groups have continued unabated. The elections that the junta says it eventually wants appear as far away as ever.

Although the economic chaos left by the Peronist government the junta ousted has lessened on paper, workers are growing increasingly restive under continued wage controls and restraints on union activity.

Under the junta's original game plan, drawn up at the time of the 1976 coup, the three armed forces commanders were to decide jointly the big questions and a retired officer, dubbed the "fourth man," would be selected president to handle administrative matters.

The internal situation was felt to be so volatile, however, that they decided to postpone selection of the fourth man and allow Videla to serve as both army head and president until things calmed down.

Although Massera told a group of journalists last month that "conditions now exist to appoint a new president," Videla shows no signs of budging. Historically, the commander of army troops has been the most powerful man here.

The navy, and many others in Argentina, maintain that Videla, described as "not a bad man, but ineffectual," is controlled by his hardline generals. His double role as army commander and president, essentially means he cannot be overruled by the others. Thus, Massera has begun taking his case outside junta meeting rooms.

One of the first persons the navy officers asked to meet with in the United States was Laurence Birns, director of the New York-based Council on Hemispheric Affairs, a human rights and political pressure group. Last month, a council report labeled Argentina the worst violator of human rights in the Americas, saying an estimated 18,000 political prisoners are held here.

What the captains wanted, Birns said later, was for the Carter administration to "see the Argentine navy as a human rights alternative."

"They said the navy was willing to publish the list of prisoners prior to Vance's visit, but that Videla had told them he couldn't," he said. The reason for Videla's refusal, Birns said they told him, was that not even Videla has the complete list. The hardline generals, who actually pick up the prisoners and hold them in sealed-off military camps, refuse to give Videla the list, according to this account.

According to an Argentine Embassy spokesman in Washington, the captains were not on an official mission and the embassy had no knowledge of their visit.