Argentina hinged its battle for the Falkland Islands today on the power of its Air Force to drive British warships and troops away from the islands' rocky coastline.

In official communiques and richly detailed accounts provided unofficially by military spokesmen following initial British actions this morning, the government described an enemy force of warships and men trapped by this afternoon in the Falkland Sound, the narrow sea channel between the main east and west islands.

After allowing the British force to enter the channel uncontested, officials said, Argentine forces at San Carlos, at the north end of East Falkland, battled a landing force of British commandos and downed several helicopters. Meanwhile, military officials said, the Air Force launched two counterattacks on eight British frigates in the channel or nearby, saying two "could have sunk" and two more were severely damaged.

Military officials gave little indication of British attacks or landings elsewhere on the islands. There were no official reports of Argentine losses. Instead, early reports focused on the attacks of the Air Force, Argentina's strongest advantage over the British task force and the key element in the military junta's defense strategy.

As British forces moved toward the islands early this morning, the Air Force commander, Gen. Basilio Lami Dozo, flew to the air base of Trelew near the southern mainland coast. There, he ordered Argentine pilots to "grit your teeth and close your fists with a hot heart and a cold mind . . . we are going to achieve victory because our cause is just," according to reports from the area.

On returning to Buenos Aires tonight, Lami Dozo declared that his evaluation of the attack had been "very positive," and added: "We have the planes to continue having the same fighting capacity that we had at the beginning. We are ready for whatever other attack on the island."

Lami Dozo soon proved to be practically the only visible government leader. The president, Gen. Leopoldo Galtieri, and the government's top military and diplomatic ranks were engaged in private meetings at the presidential palace and military headquarters.

Tonight Defense Minister Amadeo Frugoli said in a television interview that Britain "has suffered and is suffering important losses of material and of lives." Frugoli indicated that there had been a British landing on the islands but quickly added, "Landing isn't everything . . . You have to guarantee the positions, and this is what they the British have not achieved by any means."

At the Foreign Ministry, officials offered little hope of a quick diplomatic end to the fighting. A meeting of the government's working group on negotiations was canceled this morning without explanation. After attending the funeral of a former foreign minister, Foreign Minister Nicanor Costa Mendez hurried to a meeting with Galtieri and other military officials.

Buenos Aires, far north of the fighting, remained tranquil as the long-anticipated "final battle" for the Falklands was reported to have begun. After weeks of extensive accounts in print and picture of the preparedness of Argentine forces and the impossibility of a successful British invasion, crowds around kiosks and newspaper offices downtown showed a confident nonchalance.

The military command delivered its reports of the fighting on a national linkup of radio and television. The news was read by a disembodied voice behind a fixed military emblem on television, accompanied by a martial theme song.

After issuing a series of communiques this morning describing the British assault and the first Argentine air counterattack, the joint chiefs of staff--which has replaced the ruling junta as the official source of communiques--released an announcement early this afternoon that "in the future, communiques will have the purpose of ordering and clarifying events. Thus, they will be drawn out over the time necessary and sufficient to complete this objective."

Following that, the stream of official announcements halted and did not resume until tonight, when a brief communique was issued conceding the loss of three Argentine planes and damage to three helicopters.

Buenos Aires newspapers and radio stations did not hesitate to fill the information gap, however, with increasingly sensational reports of the fighting. By late in the day, news services once again were reporting the probable loss of most of Britain's air coverage, and further Argentine attacks that were said to have scored direct hits on a sixth British frigate.

Newspapers and private radio stations were also quick to relay full reports from London of accounts of the fighting, despite the nominal ban on such information decreed several weeks ago by the military junta. The media highlighted the Air Force counterattacks, however, and made no mention of the possibility of a successful British landing.

At noon, by now familiar crowds gathered on the fashionable downtown pedestrian avenue called Florida to watch bulletins in a newspaper's display windows. But the city's workers appeared to have grown accustomed to war reports during the last week, and an even larger crowd gathered one block away from the news headlines to watch a crew tear down a building.

Reports by military officials in both Buenos Aires and London indicated that Argentina's initial air attack today depended in part on small Argentine-built Pucaras and some of the Navy's eight Italian-made Aermacchi planes, another small plane designed primarily for training. Military analysts here speculated that both the Pucaras and the Aermacchis were based at Argentine airstrips on the Falklands and were filling in for more sophisticated warplanes that had not yet arrived from the mainland, nearly 400 miles away.

Later reports made clear that heavy warplanes including advanced Mirages engaged in the second battle, although it was unclear how effective the military command actually had been in mobilizing the extensive air forces along the Argentine coast.

In past air battles over the Falklands, Argentina's Mirages and French-made Super Etendards reportedly had trouble reaching battle zones without facing problems of fuel supply and bad South Atlantic weather. Many of Argentina's American-made A4 Skyhawks are reported to be based on the aging aircraft carrier 25th of May, which is believed by analysts here to have remained close to the mainland.

The private Argentine news service Noticias Argentinas quoted one military source as saying this morning that bad weather conditions in the South Atlantic had persisted and that it was possible that Argentine planes had trouble reaching the area from the mainland this morning, even though British Sea Harriers and Argentine planes on the island could operate. A later report by the agency said flying conditions had improved.

Britain's two aircraft carriers, the Invincible and the Hermes, were reported by military officials here to have been sighted about 100 miles off the coast of the Falklands, comfortably out of the range of the land-based air forces.

Diplomatic officials said they expected the next attempt at a peace settlement to be made by the United Nations Security Council. Costa Mendez left early Saturday morning for New York for a formal meeting of the body. At the airport, he said, "We are not going to ask for anything special; we're going to denounce the aggression" of Britain.

Officials noted that Argentina has expected little from the Security Council because of the veto power of Britain and, on Argentina's behalf, the Soviet Union.

The Soviet ambassador in Buenos Aires, Sergei Striganov, met with Costa Mendez at the Foreign Ministry today and told reporters upon leaving that the Kremlin maintains "solidarity with Argentina" and that "the Soviet Union deplores this new aggression by Great Britain."

The day's events apparently left pending Argentina's response to the only peace plan still available, which was forwarded last night to Buenos Aires by Peruvian President Fernando Belaunde Terry.

The Argentine military command issued a communique late tonight saying that "in effect, England has responded to the real possibility of continuing the negotiations with the initiation of an attack on the islands, the results of which are unpredictable, although without doubt [they will be] extremely bloody."

The government appeared to be focusing its efforts on lining up support against Britain among Latin American countries. Ambassadors were called to the Foreign Ministry today for a briefing on the new military action, and there were indications that Argentina was seeking to measure possible support for sanctions by the 22 American countries who adhere to the Inter-American Treaty of Reciprocal Assistance, or Rio Treaty.

In the past, Argentina has deferred calling for sanctions against Britain under the Rio Treaty because of the strong opposition of the United States and the unwillingness of many Latin American nations to take concrete action against Britain.

Argentina seems to be gaining stronger support from some of those countries tonight as the Colombian ambassador here, Vicente Borrero Restrepo, announced that his government, which abstained from supporting Argentina in the last meeting of the Rio Treaty countries, now had a "greater understanding in areas of common concern" with Argentina.