Argentina has bolstered its South Atlantic fighting force with new supplies of warplanes, missiles and rockets after a worldwide arms gathering mission aided by Latin American nations as well as Israel and Libya, according to Argentine military and Western diplomatic sources here.

During the past several weeks, Argentina has received munitions, spare parts, and rockets from Peru and Venezuela, and French-made Exocet air-to-surface missiles, probably from Iraq via Libya, these sources said.

Two Western diplomatic sources also said that Argentina had received 24 American-made A4 Skyhawk fighter-bombers from Israel. Argentine sources, while not confirming this report, said that Argentina had received a small number of fresh planes from third countries and two surveillance planes from Brazil.

Israeli officials have denied supplying Argentina with warplanes since Argentina invaded the Falkland Islands April 2. The transfer of Skyhawk planes from Israel to Argentina would violate U.S. stipulations against transfer of arms sold abroad.

Argentina has sought to purchase arms from a wide variety of countries and markets in an effort to replace the heavy losses of materiel it has suffered in more than six weeks of fighting with Britain in the South Atlantic. Argentine sources indicated, however, that the resupply effort has been difficult and not completely successful.

"We have been looking everywhere, and we have been buying from anyone who will sell," an informed Argentine government official said in an interview. "But it has been very difficult, and we have not been able to get all we wanted."

Sources said Argentina has been inhibited in its arms search by the unwillingness of Latin American countries to supply such items as warplanes and the difficulty of adapting new missile or other weapons systems to existing Argentine equipment and of training personnel to use them.

Diplomatic sources also said they doubted that the new supplies would affect the outcome of fighting between British and Argentine forces on the Falkland Islands or substantially help Argentina's military command in its announced intention to carry on the war even if the "battle" of the Falklands is lost.

Despite the new weapons, the Argentine Air Force, which has carried the brunt of the fight against British troops and ships until now, recently reported to the military command that its fighting capacity was down by nearly 30 percent, according to a high-ranking Argentine military official.

It was not clear if this percentage included planes that had suffered breakdowns or damage during the conflict, as well as those that had been shot down. But the figure, which the source said applied to the high-performance warplanes of the Air Force, would represent losses far higher than Argentina has admitted and close to the approximately 40 top planes that Britain claimed to have downed in action up until yesterday's air battles.

In recent weeks, Argentine President Leopoldo Galtieri and other ranking military leaders have openly proclaimed their willingness to accept arms supplies from abroad to fight Britain from any country willing to supply them. Air Force Commander in Chief Basilio Lami Dozo, like many military officials, has also hinted that Argentina would accept aid from the Soviet Union, if necessary.

According to two ranking Argentine military sources directly involved in the planning of military operations, however, the Argentine junta made a firm decision as the conflict with Britain worsened in April not to accept military aid from the Soviet Union. Even as Galtieri and other officials dropped hints of buying from Moscow, the decision against such purchases was privately communicated to the governments of friendly Western nations in mid-May, diplomatic sources said.

Although Soviet technicians have long been at work in Argentina on a hydroelectric project and in such industries as fishing, and some are stationed in the town of Bahia Blanca near a major Argentine naval base, the two military officials and another ranking government source denied that Soviet advisers were at work on any military-related project or that any such arrangement currently was under serious consideration.

One Western diplomatic source said it was believed that the Soviets were helping Argentina expand its radar defense system along its southern coast. But the military official said the high command saw no need for such a project, although there were some gaps in Argentina's coastal radar coverage.

Argentine sources said that the Argentine military command believes that there is almost no prospect of British air strikes against Argentine mainland bases and that the Air Force, the service in charge of the coastal radar defense system, was the element of the armed forces most opposed to any military involvement with the Soviet Union.

According to diplomatic sources, Argentina's most important new supplies have been the delivery of Skyhawks from Israel and two commercial planeloads of arms that have arrived from Libya. Military and diplomatic sources said that the country's most abundant new arms supplies have been spare parts for its planes, munitions and rockets, and that Argentina had also received new copies of the French-made air-to-sea Exocet missiles used to sink the British destroyer Sheffield and the troop transport Atlantic Conveyer.

According to both Argentine and British accounts of the fighting in the South Atlantic, Argentina would now have used up its entire original supply of Exocets in the attacks on the Sheffield, the Atlantic Conveyer, and the aircraft carrier Invincible. The new missiles were reported by one source to have been carried in a shipment of arms from Libya transported by two Boeing 707 jets appropriated by the military from the state-owned airline Aerolineas Argentinas.

The source also added that the missiles, believed to number as many as six, were believed to have come from Iraq, which bought them from France but has been unable to use them in its war against Iran. Other sources said that Argentina could have obtained the Exocets instead from Peru, although some reports have said that Peru has only sea-to-sea Exocets that are not adaptable to Argentine equipment.

Argentine military sources said other less sophisticated missiles, rockets, and spare parts have been provided to Argentina by both Venezuela and Peru. The material had been granted "as kind of a loan," one source said, and Argentina had not had to pay for the material immediately.

Diplomatic sources also said that when the conflict between Argentina and Britain began, Israel was still fulfilling the end of arms contracts it had with the military government and was negotiating on other sales.

Diplomatic sources said that despite the willingness of Latin American governments such as Peru and Venezuela to help Argentina, these governments could not deliver major supplies of planes or missiles to Argentina without seriously depleting their own defenses.