SEOUL, DEC. 22 -- South Korean President-elect Roh Tae Woo said today that he is "ready to go" to Beijing to work for improved ties between South Korea and China, which he described as "almost a necessity" for both countries.

Roh, scheduled to be inaugurated Feb. 25, would not say whether he has received any encouragement from China. But he said he believes China wants better relations despite its close ties to South Korea's arch-enemy, communist North Korea.

"I think the People's Republic of China would like to have more developed relations with us, and they seem to have moved beyond thinking only of North Korea," Roh said in an interview.

Roh, ruling party leader and a retired general, was elected with a 36.6 percent plurality last Wednesday in South Korea's first direct presidential election in 16 years. Roh is a close ally of incumbent President Chun Doo Hwan and his opponents have questioned his commitment to democracy.

Speaking softly and looking relaxed in his party office, Roh said he will investigate past corruption, rein in South Korea's security agencies and generally promote democratic reform.

"Many changes have already taken place, and we are still in the process of changing," Roh said. "If anyone doesn't see change at this point and doesn't expect change will happen, I think he or she is looking somewhere else."

During the campaign, Roh promised to instruct South Korea's widely feared internal security agencies to focus on external threats. He said today he will keep that promise.

"All these intelligence agencies should confine their activities to a strict sense of national security, and should not interfere with politics or the economy," he said, adding, "Surveillance of any politician, whether he is from the opposition or the ruling party, is not very desirable."

Roh said he would not necessarily reduce the agencies' size, saying funds could be diverted to more proper activities.

Asked whether he would investigate reports of corruption among Chun's relatives, Roh said he has heard many "unfounded and false rumors" but no "formal charges." He added: "I said there should be no sanctuary for corrupt practices, nor for persons involved in corruption."

Roh's victory has been challenged by his two chief rivals, opposition leaders Kim Dae Jung and Kim Young Sam. The two Kims, who split the antigovernment vote, have charged that the government committed widespread fraud to secure Roh's 2 million-vote margin.

Roh said today that he won fairly.

"Despite many pessimistic predictions, we have just seen an election in which every candidate and party had a fair chance to compete," Roh said.

The ruling party's confidence has grown as public opinion seems to have lined up against the Kims, whom many voters blame for failing to unite before the election. After ordering its supporters not to celebrate openly, the winning side has scheduled a belated victory party for Wednesday.

Roh has tried to maintain his image as a "common man." The victory party will be at an exhibition hall on the city's outskirts, not in a fancy downtown hotel. Taxi drivers and barbers will be guests of honor, and soju, the cheap national liquor, will be served.

"The style of government will be different," Roh said.

During today's interview, Roh also made these points: Without commenting directly on the presence of U.S. nuclear weapons in South Korea, Roh labeled the opposition's call for denuclearization as "simply unrealistic and meaningless."

"Just across the North Korean border, China and the Soviet Union are deploying nuclear arms . . . and the Korean Peninsula is under nuclear threat from those forces," Roh said. "Therefore, unilateral denuclearization, if it is not reciprocated by similar measures in China and the Soviet Union, is very unrealistic and very naive."The United States should think "strategically" as well as "commercially" before pressing South Korea too hard on trade issues, Roh said. This nation's trade surplus with the United States has grown sharply in recent years.

"I think too much pressure would not be in the interest of either country," Roh said. "It would be very harmful."Roh repeated his promise to put his record before the public for a vote of confidence after next September's Olympic Games here. But he said the vote, which he made as part of a general promise during the campaign, might be simply a vote of confidence in the National Assembly.

"If that assembly was selected as a result of a fair and open election, I think it can be used. There can be no objection to that," Roh said. "What I want to see is how the Korean people render judgment on my record . . . . There can be other ways, too."

Roh's opening to China would mark a sharp departure from historic policy. China fought alongside North Korea during the 1950-53 Korean War while the United States joined forces with the South.

China and South Korea have no official ties. But the two nations have increased their trade through third parties and directly, through unofficial channels, in recent years. It is now believed to amount to more than $1 billion per year.

In addition, China has made it clear that it intends to participate in next year's Seoul Olympics.

Roh said he believed improved relations would defuse tensions on the Korean Peninsula.

"I think this is a natural tendency that will result in mutual benefit, strategically by exercising a check on the adventurism of North Korea," he said.