South Korea and the United States will announce agreement this week to have Tongsun Park interviewed in the U.S. embassy here, sources said here today.

The sources said, however, that an arrangement for a detailed interrogation of Park is not yet in sight and may take a long time to negotiate even if he is willing to submit to questioning.

A date for Park's preliminary interview was not disclosed, but Seoul newspapers, quoting government sources, said it may be this week or next.

The preliminary interview was agreed on after a week of negotiations here between U.S. Ambassador Richard Sneider and South Korean Foreign Minister Park Tong Jin.

Aides today were putting the finishing touches on the agreement.Among the final details to be worked out was the question of whether South Korean officials will be present. It could not be learned whether Justice Department officials would come here for the preliminary interview.

Park will be asked whether he will return to the United States or go to a third neutral country to give testimony about the Congressional lobbying scandal, sources said. Park has been indicted by a federal grand jury that charged he acted on behalf of the South Korean government in making payments to Congressmen to influence their voting.

Park so far has refused to return to the United States. The South Korean government, despite a request for co-operation from President Carter, has conditions - when the interview said that it will not force him to return.

A week ago, however, the foreign minister said he had submitted a new proposal to the U.S. Ambassador, hinting at a limited degree of cooperation in making Park available. The would take place, who would be present, and how long Park would be questioned - have been the subject of negotiations.

Even lengthier ones would be required to get Park before any panel for thorough interrogation on his and the government's role in seeking influence in Congress for continued U.S. aid to South Korea, the sources said.

For the first time in the affair, government sources are suggesting through Seoul newspapers that a trip out of the country for Park is not out of the question.

That has been interpreted to mean that the government might permit him to go to a neutral country to give testimony in some form.

Whatever was worked out would be included in a special "mutual assistance prosecution agreement" signed by representatives of both countries, the sources said. There is also the possibility, they conceded, that Park will simply refuse once again to leave South Korean.

The South Korean government's new approach is regarded as its reaction to the renewed threat in Congress to reduce military aid. A bill providing for the transfer of U.S. miltary equipment to South Korean forces when American troops withdraw already has been shelved until next year because sponsors said it could not pass in the current mood of hostility over the Park affair.