With a terse, one-sentence statement that may have serious repercussions for U.S. - South Korean relations prosecutors for the two countries admitted failure today in their attempts to find a mutually acceptable way to question accused Korean agent Tongsun Park.

"We have been unable to reach agreement," a spokesman said, as the three grim-faced American negotiators quickly left the talks site for a waiting plane back to Washington.

The abrupt and unsuccessful end to the 3 1/2 days of talks is likely to trigger attempts in Congress to cut U.S. aid to Korea. It also puts further criminal prosecutions in extreme doubt because of Park's unavailability as a witness.

Park has been charged in a 36-count felony indictment as being a key figure in a South Korean government-sponsored scheme to influence members of Congress with cash and gifts. The former Washington businessman and dinner club owner left the United States for London last fall and has been in Seoul since August.

Benjamin R. Civiletti, head of the Justice Department's criminal division, declined to answer substantive questions about the issues that divided the two sides.

But it is known that he planned to make clear to the Korean negotiators during the talks that a report of lack of cooperation would create adverse effects in Washington.

It is also known that the Justice Department officials felt they could accept nothing less than an agreement to let them question Tongsun Park in Korea under conditions admissible in an American court.

This would have entailed bringing federal grand jury members to Korea to witness the questioning and providing an opportunity for defense attorneys to cross-examine Park here.

The Koreans, on the hand, had said publicily that they might have accepted a so-called "Blockheed solution." This is a reference to the occasion when Japanese prosecutors went to California to sit in on questioning of a Lockheed Aircraft CO., executive involved in the kickback scandal on the sale of planes to Japan.

While testimony from such an agreement was acceptable in a Japanese court, it would not be admissible in the United States.

Though neither side would confirm it today, the key isue seemed to be who would control a Tongsun Park interview. The Koreans apparently were unable to compromise even enough to satisfy the American's technical legal requirements.

All during the talks, Korean government officials not involved in the discussions have referred to the need to maintain Korea sovereignty, to "save face" to not appear to be buckling under U.S. pressure.

Civiletti and his two companions, Paul Michel, the attorney in charge of the Korean influence buying investigation and Allan Meyer, Michel's FBI counterpart, realized the sensitivity of the Korean position, but they were willing to make the effort to question Park. Civiletti said before the negotiations started, because Park was so important to their inquiry.

So far, only Park, Hancho C. Kim, another Korean businessman in Washington and former Rep. Richard T. Hanna (D-Cal.) have been indicted in connection with the case. Payments Park made to Hanna were by check and therefore easily traceable. Park usually made other payments to U.S. officials in cash with only himself and the recipient as witnesses.

Without his testimony, therefore, evidence of such payments is lacking and further criminal indictments are unlikely in the forseeable future.

A more immediate effect of the failure of the talks is expected to be renewed volley of criticism from Congress toward the Korean government's lack of cooperation in the investigations.

Leon Jaworski, special counsel to the House Committee on Standards of Official Conduct, which is checking reports of misconduct by individual House members, did as much yesterday. In his opening statement at public hearings on the Korean lobbying campaign, the former Watergate special prosecutor charged the Koreans with obstructing the committee investigation.

Their invitation for Jaworski to interview Tongsun Park in Korea was so laced with restrictions as to "make a farce" of the committee's efforts, he said.

Rep. Bruce F. Caputo (R-N.Y.), a member of the committee, narrowly lost a vote last month that would have directed a cut in U.S. aid to Korea because of the Seoul government's reluctance to make Park available.

Congress this week passed the Administration's $6.8 billion foreign aid bill whichincludes $280.4 million in military aid to Korea.