Britain reported downing at least six Argentine warplanes yesterday as Argentina resumed its air counterattack against British forces seeking to expand their foothold on the Falkland Islands.

The British Defense Ministry said one of its frigates suffered "some damage" in a series of raids launched by the Argentine Air Force against ships in the inlet off San Carlos, where about 5,000 British troops landed Friday morning. It was the first Argentine air attack since Friday, when warplanes damaged five British ships but lost a total of 20 aircraft, according to Britain.

Britain also reported that its planes downed at least one Argentine helicopter in a separate incident yesterday. Neither side gave casualty figures for the day's fighting.

Argentina's high command confirmed in a communique last night that the air attack had taken place but gave no details. Unofficial reports from Buenos Aires said Argentine aircraft "seriously damaged" three British ships in the raid and also said Argentine ground forces had begun an offensive against British troops ashore. The high command, which maintained a news blackout throughout most of the day, did not confirm these accounts.

There were indications in London that British ground forces intended to move swiftly to retake the islands. British Foreign Secretary Francis Pym, in an interview with ABC-TV, predicted victory for British troops. Conservative Party chairman Cecil Parkinson, a member of Prime Minister Margaret Thatcher's inner "war cabinet," said Britain was "not looking for a long and bloody war."

In Washington, Secretary of State Alexander M. Haig Jr., in a CBS-TV interview, reaffirmed U.S. support for Britain and said he believed a diplomatic solution to the South Atlantic conflict was unlikely until one side or the other gained a clear military advantage.

The United Nations Security Council met for the third day of an emergency session called to search for a peaceful resolution of the conflict. No action was taken, and the meeting was adjourned until Monday morning.

Argentine President Leopoldo Galtieri, responding to Pope John Paul II's call for an immediate cease-fire and resumption of peace talks, sent a message to the pontiff declaring Argentina's willingness to stop the fighting. But Galtieri also indicated that Buenos Aires had no intention of backing away from its claim of sovereignty over the disputed islands, which it seized from Britain on April 2.

Yesterday's fighting followed a one-day lull in Argentina's air attack that analysts said may have been caused by poor weather and that gave British forces an opportunity to consolidate their 10-square-mile perimeter in the northwest corner of East Falkland Island.

The lull ended early in the afternoon with raids by an unspecified number of Argentine warplanes. British Defense Ministry spokesman Ian McDonald said five French-built Mirage jets and one American-made Skyhawk were shot down by missiles fired from surface vessels, shore-based antiaircraft installations and Sea Harrier jets. He said another Mirage and two other Skyhawks "were probably shot down."

Independent Television News reporter Jeremy Hands, with the British fleet, said the attacking planes "came in very low; they flew very fast."

Robert Fox, a British Broadcasting Corp. reporter who witnessed the downing of one warplane, said he saw "an enormous ball of fire with black smoke coming out of it as the Skyhawk hit the water."

McDonald said he had no indication of the extent of the damage to the frigate nor whether there were casualties. He said he also had no reports of damage to other British ships or aircraft.

In an earlier incident, he said, Sea Harriers attacked three Argentine helicopters in the Falkland Sound off the coast of West Falkland Island. McDonald said one Puma helicopter was destroyed, a Bell helicopter was set afire and a second Puma may also have been damaged.

The British Defense Ministry also said yesterday that British jets bombed and strafed an Argentine airfield near Goose Green on Saturday, wrecking several planes and setting an Argentine vessel afire. There were unconfirmed reports last night that British ground forces had taken Goose Green.

The ministry said a British frigate ran an Argentine supply boat aground Saturday. The crew reportedly abandoned ship and there were no reports on casualties.

The fighting yesterday brought total Argentine losses of warplanes and helicopters in the last three days to at least 27, according to British reports. Overall, Argentina is believed by British military analysts to have lost 58 planes and helicopters since fighting in the South Atlantic began, more than a quarter of its estimated 220 aircraft. Argentina has acknowledged losing six warplanes since Friday.

Britain has reported 48 dead, one missing and 55 injured since Friday. Six British warships have been reported damaged since Friday. One of them, the frigate Ardent, was sunk with the loss of 22 seamen. Argentina has insisted that eight British warships were heavily damaged Friday, with two of them sunk.