TOKYO, FEB. 11 -- South Korean President-elect Roh Tae Woo, continuing his effort to distance himself from past authoritarian regimes, today announced the appointment of a university professor with no political experience as his prime minister.

Roh, elected last December in the nation's first free vote in 16 years, announced that Lee Hyun Jae, 58, an economist and former president of Seoul National University, will become premier when Roh is inaugurated Feb. 25. Roh's spokesman said that Lee offers a "fresh image to begin again as a new republic."

The prime ministership traditionally has not been a powerful post in South Korea. But by choosing a political novice with a reputation as a moderate in handling student demonstrations, Roh used the closely watched appointment to demonstrate that, although he is a retired general and leader of the ruling party, he will offer more than a continuation of the current unpopular regime which was installed by the military.

The appointment comes as Roh unexpectedly faces the possibility that the nation's chief opposition parties may unite in time for National Assembly elections this spring. The opposition split in the Dec. 16 election, allowing Roh to win with a 37 percent plurality, and continued squabbling had suggested that he would enjoy the same advantage to take control of the legislature.

But the surprise resignation Monday of opposition leader Kim Young Sam has given new impetus to the opposition to form a coalition. Leaders of the two main opposition parties met today and pledged renewed efforts to unite.

Kim and his longtime rival opposition leader, Kim Dae Jung, both ran for president and together polled 55 percent of the vote, with Kim Young Sam coming in slightly ahead to finish second. The two Kims, who struggled against authoritarian governments in uneasy coalition for 20 years, bitterly blame each other for squandering the opportunity of the December election, and they have not met since.

But Kim Young Sam's sudden resignation as president of the Reunification Democratic Party has put pressure on Kim Dae Jung, head of the breakaway Party for Peace and Democracy, to follow suit. A number of Kim Dae Jung's followers and independent opposition activists are threatening to join the Reunification Democrats if Kim Dae Jung does not step down.

Kim so far has resisted calls for his resignation or for a merger of the two parties before the legislative elections, now expected in late March or early April. But one of his lieutenants, Lee Joong Jae, met with senior Reunification Democratic officials today and said afterward that "an opposition merger is a call of the era." However, the 13 officials from the two parties made little progress in what they said was the first of a series of meetings aiming at a merger.

Analysts in Seoul believe that if the two opposition parties remain split, Roh's ruling Democratic Justice Party could easily maintain control of the National Assembly, which his aides regard as a priority. If they merge, the outcome would be much more difficult to predict.

Roh has been taking every opportunity since his election to show that he can inaugurate a new era of democracy. His appointment of Lee as prime minister will further this "fresh impression to the people," a government spokesman said.

Lee graduated from South Korea's top university, Seoul National, in 1953 and served as its president from 1983 until 1985. A knowledgeable source said that Lee resigned as the university's president because he opposed demands from the powerful security agency to take stronger disciplinary action against students involved in the takeover of a USIA building in Seoul.