FBI Director William H. Webster yesterday acknowledged that agents have interviewed U.S. citizens returning from visits to Nicaragua, but said the interviews were for legitimate "foreign counterintelligence" and not to harass opponents of administration support for "contra" rebels.

Webster told a House subcommittee that there were approximately 100 interviews and that they were not intended to "prevent people from going to Nicaragua or make them sorry they went to Nicaragua."

But Rep. John Conyers Jr. (D-Mich.) suggested that the FBI visits were intimidating. And Jerry Berman, an American Civil Liberties Union lawyer, suggested that the real purpose of the visits was to "chill speech" using "down-and-dirty political games."

Berman said Webster's reasons are subject to challenge because many of those interviewed oppose administration policy, and therefore are not likely to provide the FBI with useful intelligence.

The hearing by the House subcommittee on civil and constitutional rights grew out of complaints from travelers to Nicaragua who contacted the Center for Constitutional Rights in New York after being questioned by FBI agents. The center then contacted the subcommittee.

About a dozen of those contacted by the FBI are members of the Central American Solidarity Coalition, a group that works closely with the Sanctuary Movement, which smuggles Central American refugees into the United States. Members regularly travel to Nicaragua on "fact-finding missions" and attempt to "mobilize public support against the administration's policies in Nicaragua," Thomas Cannon, an attorney for the group, said in an interview.

Daisy Cubias of Milwaukee, a member of the group, said in an interview that FBI agents visited her once at her place of employment and twice at her home after she visited Nicaragua.

During the first visit -- on Jan. 3 at her home -- Cubias said she was asked whether any members of her group were "involved in terrorism." Cubias said she told them her group was "concerned with peace, not terrorism."

According to Cubias, the agents told her that a number of members of her group were being investigated. The agents mentioned names, Cubias said, and "I told them to go talk to those people then. They said that they couldn't because those people wanted to see their lawyers."

Cannon said another group member refused to speak to an agent without a lawyer, and was warned by the agent that certain members of the group might be sympathetic to the Soviet Union.

Social worker Amy Good, another group member, said she went home March 19 and found a note in her mailbox. It said, "Amy, could you contact me at this phone number?" The note was signed, "John T. Andrews."

Good said that she dialed the number and that a voice answered, "FBI."

"I hung up," she said.

Good said she went to Nicaragua in October for 12 days as a volunteer member of the Witness for Peace program. There, she said, she "talked to people and tried to learn as much as I could about life in Nicaragua."

When she returned, she said, she gave numerous talks and slide shows on college campuses and at church organizations. Her message, she said, was that contra rebels supported by the Reagan administration and fighting the Nicaraguan government "brutally attack civilians and medical and educational centers. They're not constructive at all. They're just murderers. We shouldn't be supporting them at all."

Of Webster's statement that the FBI is gathering foreign counterintelligence, she said, "Anything they wanted to know, all they had to do was come to one of the meetings where I speak. I feel like it's harassment, like they're trying to get people to stop doing the work that they're doing."

But at least one of those contacted by the FBI did not visit Nicaragua, according to the Center for Constitutional Rights. David Rostan, a law student in New York, found a business card in his mailbox in March. The card said, "Please call me about Nicaragua. This will be a friendly chat." It was signed by an FBI agent.

Rostan did not call the agent. He has said that he might have been contacted because he attended a meeting about Nicaragua at City University of New York.

Webster said yesterday that he had "difficulty understanding" those who suggest that the FBI should not interview persons who had traveled to Nicaragua. "We're carrying out an important function for the U.S. government," Webster said, adding that his agents had not threatened or intimidated anyone.

Conyers replied, "That's the most amazing thing I've heard this morning, Judge Webster . . . . For you to tell me that no one should be intimidated by a little friendly visit from a polite FBI agent who left his card . . . . "

Webster said he did not think Conyers was speaking "to the point," adding, "I never grew up in an atmosphere where a visit from an FBI agent in and of itself was some kind of threat . . . . "

"I grew up in Detroit," Conyers replied. "An FBI visit to a job, sir, can destroy a person's career . . . . It's not the kind of thing that makes a person popular in his job or at home. Let's get real this morning: Friendly visits from the FBI are no good. They're not welcome in our society."

Later, Webster testified that FBI agents were asked to perform the interviews by the Central Intelligence Agency and the National Security Council.

"From time to time we will receive requests from the director of counterintelligence or the National Security Council expressing an interest in certain things that may be taking place that affect our national security," Webster said.

"We have gotten no instigation from anybody to make life miserable for people trafficking back and forth to Nicaragua," he added.

Webster said FBI agents also routinely interview U.S. citizens who travel to other countries.