South Korea's interim government announced today that it intends to elect a successor to slain president Park Chung Hee under the pesent constitution.

Announcing the decision in Seoul, Acting President Choi Kyu Hah said he believes the successor should not serve out the five remaining years of Park's term.

Instead, Choi said, the new president should call for new elections under an amended constitution "as soon as realistically possible."

He said this arrangement would provide both for stability and for "a steady progress of democracy in this country."

Choi did not mention himself as a likely candidate, but it is believed that he will be the choice of a wide spectrum of politicians who had supported Park. His supporters also claim that Choi is favored by military leaders who have gained influence under martial law imposed after Park's assassination.

Opposition leaders had wanted the constitution amended before choosing Park's successor so that the new president would be chosen in a direct national election.

Under the present constitutional system the successor will be chosen by the National Council of Unification, the same national body that last year had chosen Park for a new six-year term. Most of its members reflect the views of the late president.

The election must be held by Jan. 25 to make it fall within the prescribed 90 days after the presidenths death. Park's replacement would be entitled by law to serve the rest of Park's term, nearly five years.

But Choi said the new president shoudl not serve the entire remainder of Park's term but should call for a new election under an amended constitution after consulting with a diverse group of South Koreans.

"I am confident that this will be the most reasonable way of meeting the wishes of the people for stability and eventually a steady progress of democracy in this country while maintaining constitutional order," Choi said.

The acting president, a close friend of the slain president, warned that the North Korean communists would like to take the opportunity of Park's assassination to cause division in South Korea and prepare for a military attack.

Meanwhile, South Korea's opposition party decided Friday that it will return to the National Assembly next week in a move that it hopes will block military leaders from retaining control of the government.

A caucus of the New Democratic Party also passed resolutions calling for the release of all political prisoners and for a withdrawal of the emergency decree that had been used by Park to jail political dissidents.

All 66 members of the New Democratic Party had resigned from the National Assembly in early October aafter their president, Kim Young Sam, was expelled on Park's orders for his strong criticism of Park's government.

Its member had privately expressed concern this week that unless that parliament is restored as an influential force the vacuum would be filled by the military, which already has attained considerable power as a result of a martial law imposed after Park's assassination.

That concern came to the surface after the party caucus Friday as Kim warned of military influence.

"If the present political vacuum is prolonged, the politics of this country go into the hands of the military," Kim said in a comment after the party caucus.

"We have decided to end the boycotting because we believe in parlimentary politics based on democracy." Kim said.