Boston police yesterday arrested three persons for disorderly conduct after they allegedly tried to block a truck from crossing a picket line erected by striking Boston University (B.U.) clerical workers and librarians.

Those arrested were Timothy S. Chamberlain, a member of the clerical workers' union; Karyn Peloso, a B.U. freshman; and Stephen Krasner, a Brighton resident who is reportedly a friend of one of the strikers.

"The police were out to make arrests," Chamberlain said yesterday after the three were released on their own recognizance. He said he was arrested after being pushed against a policeman, and that Krasner was arrested after arguing with the policemen about Krasner's arrest. Peloso was arrested "for being a loudmouth," Chamberlain added.

"We felt we had to be forceful," Chamberlain said, adding, "the idea was not to be violent, but to be vocal." "We weren't being violent in any way, but neither were we being meek little lambs," he added.

Chamberlain said 16 policemen and two paddy wagons were present at the time of his arrest, and the 16 policemen remained later in the day when there were only two picketers at the location.

Police spokesmen said the arrests were made to prevent disruption of traffic, but they declined further comment.

Boston University is paying the City of Boston to provide 20 policemen to watch the picketers, Stephen Wagner, a B.U. spokesman, said yesterday.

Wagner said the university did not ask the police to make the arrests and that the arrested picketers would not be punished by the university.

B.U.'s 900 clerical workers and 20 librarians are striking in an effort to compel the university to recognize their two unions. The National Labor Relations Board (NLRB) certified the unions last December, but the B.U. administration has said it will not recognize or bargain with them until it has exhausted its appeal of the NLRB decision. The appeals process could take up to two years.

State Rep. Barney Frank told a rally of 250 clerical workers yesterday he will ask guest lecturers and performing artists not to provide services to the university until it agrees to open contract negotiations with the unions.

Wagner said yesterday almost all of the university's classes are now meeting as scheduled.