SEOUL, JUNE 24 (WEDNESDAY) -- President Chun Doo Hwan, seeking to end the most serious crisis in his seven-year presidency, today offered to reopen a suspended debate on constitutional reform and release from detention dissident leader Kim Dae Jung and others, an opposition leader said.

But Kim said that Chun turned down a request for a national referendum on what type of government South Korea should have and a request to free about 3,000 other persons the opposition regards as political prisoners.

Chun's decision was conveyed to Kim Young Sam, president of the main opposition party, in a three-hour emergency meeting here today following two weeks of violent street demonstrations against his government, according to Kim Young Sam.

Kim told a press conference afterward that he could not recommend that demonstrations end, because the government had not offered serious concessions.

Chun suspended constitutional debate on April 13, in a decision the ruling party had maintained was "irreversible." Public anger over the decision is believed to have helped fuel the recent demonstrations.

The president did not agree to a request from Kim to revoke the April 13 decision officially. But he did agree to reopen talks on the subject, which is what his decision on April 13 ruled out.

Newspapers with a large photo of Kim Young Sam and Chun shaking hands at Chun's office -- it was the first time they had met -- were snapped up on Seoul streets at lunch time. Street violence has subsided markedly since yesterday.

Chun responded negatively to requests to free 3,000 persons the opposition views as political prisoners and to restore the legal rights of Kim Dae Jung, Kim Young Sam indicated in the press conference.

Kim Dae Jung has been under house arrest since early April. This morning, Kim Young Sam went to his house in western Seoul and for the first time since the arrest began was able to pass through police lines for a meeting with him at his house.

Kim Young Sam said Chun promised the house arrest of Kim Dae Jung would be lifted later today.

Chun also said he was willing to release most of about 300 persons who were jailed since demonstrations began June 10, according to Kim Young Sam. But he said people involved in arson and other violent crimes could not be freed.

Chun proposed that Kim Young Sam meet with ruling party chairman Roh Tae Woo to work out details of the constitutional negotiations.

The talks between Chun and Kim were part of a series of high-level meetings among government, opposition and U.S. officials today and Thursday.

Gaston Sigur, the State Department's senior Asia expert, arrived in the capital yesterday afternoon and met with Foreign Minister Choi Kwang Soo and Cardinal Stephen Kim, leader of the country's 2 million Catholics. No details of the talks were available.

Kim Young Sam, in preparing for the meeting with Chun, had told reporters yesterday that he would seek a retraction of the April 13 decision suspending a dialogue with the opposition on reforming the constitution. He said he would demand a national referendum on how the next national leader should be elected.

The opposition has said the current system, in which the president is chosen by an electoral college, is open to manipulation by the ruling party. It wants direct election of the president, while the ruling party is proposing a parliamentary system headed by a prime minister.

"When the government guarantees that we can have a democratic government, then there won't be any demonstrations and violence," Kim Young Sam said.

Authorities reported only minor clashes in provincial cities yesterday. About 20,000 students gathered peacefully at Seoul's Yonsei University in what was said to be the largest student gathering ever held at that campus.

In Pusan city, two Catholic priests were among those injured Monday when riot police allegedly attacked a bus filled with protesters.

Chun is under extreme pressure to introduce democratic reforms. Still, yesterday he projected a business-as-usual image, leaving town for the day to officially open a pair of nuclear power plants in Yonggwang, 150 miles southeast of Seoul. There, he made his first public remarks on the crisis.

"Attempts to solve problems by resorting to violent and illegal means will serve no one's interest," he was quoted by local newspapers as saying.

Chun has said he will step down as president in February. It was the formal nomination as Chun's successor of his close associate, Roh Tae Woo, by the ruling Democratic Justice Party on June 10 that sparked the demonstrations.

The Reagan administration has been urging Chun to avoid emergency measures in coping with the crisis and to solve it through dialogue and compromise. Similar pleas have come from Capitol Hill.

Sigur's trip is seen as an effort to underscore U.S. concern over what he has said is an "obviously serious" situation. At the same time, the United States is concerned that the visit may raise anxieties about the U.S. role and suggest analogies to visits by U.S. special envoys in the final weeks of the presidency of Ferdinand E. Marcos in the Philippines.

Sigur was scheduled to meet separately with Chun, Roh Tae Woo and Kim Dae Jung today. On Thursday, he is to talk with Kim Young Sam.