At least one Argentine diesel-powered submarine may have eluded British air and sea forces and fired errant torpedoes at Royal Navy warships during the battle of the Falkland Islands, U.S. government officials said last week.

They said the admittedly fragmentary evidence on the cat-and-mouse game played under the sea during that war suggests, but does not prove, that an Argentine 209 sub built by West Germany foiled elaborate Royal Navy antisubmarine defenses.

"I can't rule it out," said one government official on the basis of after-action reports on the Falklands. "There were a lot of sonar contacts; the British fired a lot of antisubmarine ordnance. There is some evidence that a 209 was out there."

Whether a quiet 209 was able to make it into the middle of the British fleet is more than just a footnote to the miniwar over the Falkland Islands. It could become a factor in an upcoming U.S. arms decision.

Some advocates of forcing the U.S. Navy to buy updated German U-boats along with more expensive nuclear attack submarines are treating what the Pentagon considers still inconclusive reports on the Argentine sub's penetration as proof that diesel boats can still foil modern navies.

A paper attributed to but not signed by the West German shipbuilding firm of Thyssen Nordseewerke, which is trying to sell its TR1700 diesel submarines to the United States, makes that claim.

The paper, sent to Congress and at least one newspaper, states, without giving sources, that the Argentine diesel submarine San Luis, a German 209 built by Howaldtswerke Deutsche Werftill, "was at sea and submerged for over a month until she was able to attack the British squadron . . . .

"It is believed the San Luis conducted an attack on May 5 three days after sinking of Argentina's General Belgrano and fired wire-guided torpedoes against one or more targets, one supposedly the carrier Invincible."

According to this version, and fortunately for the British, an unexplained failure prevented the torpedoes from exploding.

"After the attack," the paper continues, "the San Luis was subject to continued antisubmarine attack by ships and helicopters for about 72 hours, which she could elude due to her small sonar target echo, her maneuverability and her outstanding quietness.

"The submarine returned undamaged to port. In spite of the torpedo mishap, the ship itself performed beautifully and demonstrated its efficiency pitted against one of the best ASW antisubmarine warfare organizations in NATO."

One government defense specialist, who has received the paper, said the Thyssen Nordseewerke firm based its information on reports it received from the Argentine military. Argentina has ordered six TR1700 diesel subs from the German shipbuilder and has close ties with the firm.

A high-ranking U.S. defense official said evidence exists that an Argentine 209 submarine was in range of the British fleet during the Falklands crisis, leading analysts to assume that it fired some torpedoes.

What went wrong with the torpedoes could not be learned, although they could have been duds. This was true of more than half of the bombs dropped by Argentine warplanes on British ships during the Falklands war.

Stories that an eight-year-old diesel submarine penetrated the Royal Navy's elaborate antisubmarine defenses is expected to renew congressional interest in buying this cheaper type of undersea attack boat. The nuclear-powered Los Angeles class attack submarine costs $867 million, while Nortseewerke has talked about pricing its TR1700 diesel at about $100 million.

Sen. Gary Hart (D-Colo.), a member of the Senate Armed Services Committee, has been the leading congressional adovocate of buying a mix of diesel and nuclear attack submarines for sinking other submarines or surface ships.

He has said that at least 14 diesel types should be purchased by the Navy to learn the best ways to combat these modern non-nuclear subs which, when on attack, run quietly on batteries. Who hears whom first is often decides who lives and dies in the depths.

Navy leaders have been steadfastly resisting a high-low mix of nuclear and diesel attack submarines, contending they should favor the long-distance capabilities of the nukes while allies buy the diesels for combat closer to ports.

However, Congress insisted that the Navy assess the potential of diesel submarines. The secret report, just delivered to Congress, concluded that diesels do not make sense for the U.S. Navy.

Navy Secretary John F. Lehman Jr., in a letter accompanying the report, wrote that in view of the negative findings, "I plan no additional action with regard to the further development or procurement of diesel electric submarines."