A boycott of future Soviet book fairs was threatened today by an American publishing industry spokesman if the Soviets do not give assurances that in coming years, visas will be issued without trouble to American exhibitors.

Alexander Hoffman, Chairman of the industry-wide Association of American Publishers told a press conference at the start of the one-week Second Moscow International Book Fair that "future American participation has to be considered carefully"

The Soviets denied visas to the heads of two American publishing houses that have printed dissident Soviet authors' works and delayed until the last moment the visas of many other Americans who planned to come here.

"When I return to the U.S., I intended to ask the board of directors of the AAP to weigh carefully whether American participation in future Moscow fairs is desirable or even possible unless the Soviet Union gives solid assurances that it won't use the visa as an instrument to bar or limit legitimate publishing activities," declared Hoffman.

The head of the International Publishers Association, Per Sjogren, sharply criticized the Soviets for banning South Korea from the fair and denying visas to 14 Israeli publishing officials.

"These are things we cannot take lightly. We do intend from our organization to try to make it perfectly clear to the authorities here that the cooperation of progress and that these sorts of things will not happen" he said. progress and that these sorts of things will not happend" he said

Sjorgen made his remarks at the same press conference, held at the booth sponsored by the AAP and the U.S. government. The booth contains a collection of 321 books on contemporary American life.

One book intended for the booth, political caricatures entitled, "The Art of David Levine," has been confiscated by Soviet customs agents. The number of banned American books reached 44 this afternoon, and Hoffman and other U.S. book officials have protested the seizures to Soviet censors.

The American expect a response to four specific cases they raised, but Hoffman said they had made a general protest covering all the confiscations.

Books confiscated by Soviet authorities included several by Soviet dissidents or emigres such as Alexander Solzhenitsyn, Andrei Sakhorov and Josef Stalin's daughter, Svetlana Alliluyeva and studies of Soviet society and government by Jerry Hough and Paul Hollander. Also confiscated were George Orwell's "Animal Farm," John Toland's "Adolf Hitler," and Desmond Morris' "Manwatching."

Soviet authorities said some books were banned because they did not "serve the purpose of detente and mutual understanding," others because they were "militarist and racist literature and pornography."

Sjogren asserted that the Soviets had unfairly and without cause ignored a South Korean exhibit application that he said had been properly submitted well ahead of deadline. "We must feel that all our members are treated fairly and equally, he asserted.

The American publishers barred from coming are Robert Bernstein, head of Random House Books, and Mr. and Mrs. Carl Proffer, of Ardis Press. Sjogren said, "We can't take lightly" Bernstein's absence.