The United States formally protested to South Korea yesterday "the regrettable events" surrounding the arrival of opposition leader Kim Dae Jung at the Seoul airport, seeking -- and obtaining -- assurances that his alleged manhandling will be investigated and his safety assured.

Privately, a senior administration official said the incident was "exacerbated by committed Americans" in the delegation that accompanied Kim, which included two House members and two former State Department officials.

Another official said, however, that clearly force was used against U.S. citizens and there is "no reason to believe it was a misunderstanding."

State Department deputy spokesman Edward Djerejian said U.S. officials had been discussing arrival procedures with the South Korean government for several weeks.

"We had hoped for a trouble-free return," he said, adding that Kim's advance people had agreed that he and his wife would be separated from the party at the airport and taken home. But that message apparently was never delivered to Kim's 37-member delegation.

"It appears when some of the group accompanying Mr. Kim resisted police efforts to separate them from Mr. Kim on disembarking from the plane, the Korean security officers responded with considerable force," Djerejian said.

U.S. Embassy officials who had been promised access to the plane and to the House members were not permitted to approach, "a fact which we deplore," Djerejian said. A South Korean who had been scheduled to board the plane in Tokyo and explain the procedures to Kim either did not arrive or did not provide the information, he said.

"Our embassy has protested and has asked the foreign ministry for an investigation, an explanation and guarantees of the proper treatment of the Americans accompanying Mr. Kim," Djerejian said. He added that the United States "will follow closely" the treatment Kim receives in the future.

Djerejian said Kim apparently is under house arrest. "We regret any steps, such as this one, that do not promote the goal of political development in Korea. We hope that these restrictions on Kim will be lifted as soon as possible," he said.

Another U.S. official who asked not to be named said that both Kim and his wife had minimized the airport violence, while the Americans had stressed it. He added:

"The police were violent, but the Americans seem to have made a much bigger deal out of it than Kim did, maybe for political purposes."

The senior administration official said the episode was "not planned, but neither side did what was expected."

Washington Post correspondent John Burgess reported from Seoul that U.S. Ambassador Richard E. Walker is known to have said privately that the incident was blown out of proportion and suggested that the group might have provoked the security guards' actions by linking arms.

President Chun Doo Hwan is scheduled to pay a visit to President Reagan in April, and there are no changes in those plans at the moment, officials said. The visit was not announced until State Department extracted assurances from the Korean government last week that Kim would not be harmed or imprisoned.

Rep. Edward J. Markey (D-Mass.), who accompanied Kim in a visit to House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) last week, wrote Reagan yesterday expressing outrage over the airport incident and asking Reagan to postpone Chun's visit until the investigation is completed.

O'Neill asked Reagan "to personally guarantee the safety and security of Mr. Kim and the members of Congress who are with him."

The Koreans are scheduled to host the 1988 summer Olympics, but Markey's letter said: "If two members of Congress are treated this way, how can we be assured of the safety of the athletes of the world at the Olympics?"