Soviet censors at the Moscow Book Fair confiscated more books deemed ideologically dangerous today, while the country's top publishing official declared that to do so is "the highest affirmation of freedom of speech."

Thirty-five American titles have been seized by customs agents through this afternoon.

Although some may eventually be returned for display, U.S. publishing representatives hold out little hope for many of the confiscated works, which include those of banished or suppressed Soviet writers, histories of Russia and its bitter adversary China, and works of political philosophy.

The week-long fair is scheduled to open Tuesday.

At a press conference today, Boris Stukalin, chairman of the State Committee for Publishing Houses, Printing Plants and the Book Trade, declared that to call such book-banning a violation of free speech "is not correct."

Stukalin, a full member of the Communist Party Central Committee, asserted, "This is the highest affirmation of freedom of speech since freedom to propagandize fascism is the kind of freedom that all honest people in our country and in other countries must oppose."

The 57-year-old official added: "Books of that nature do not bring people closer together and do not serve the cause of detente. Instead, they stir up hatred and hostility between people and hamper the process of detente." In the Soviet Union, all printing plants and duplicating machines, including office copiers and typewriters, are registered and legally under the control of Stukalin's bureaucracy.

The U.S.S.R., he said, has laws which "forbid the importation of certain books. We ban books that propagandize war and racism, books with an anti-Soviet character, pornography and those insulting the dignity of other participating states . . . There are very few who have brought in books contradicting our law and these will not be allowed."

The banned titles include a collection of political cartoons by New York caricaturist David Levine, works by exiled Nobel laureate Alexander Solzhenitsyn, two about defector ballet star Mikhall Baryshnikov, and a novel by dissident Soviet humorist Vladimir Voinovich, "The Life and Incredible Adventures of Ivan Chonkin," a satire of contemporary Soviet life.

At the 1977 fair, just eight U.S. books were confiscated. American publisher Lawrence Hughes, president of the William Morrow firm, speculated that "many more books are controversial this time than last because U.S. publishers have not pre-censored themselves. We publish the books. Let them censor it."

Soviet customs agents hit the Random House collection hard today, seizing 13 of several hundred books. The firm's president, Robert Bernstein has been denied a visa. Stukalin, while explaining that that was not his committee's responsibility, said, "The competent organs of the U.S. know very well why a visa was not issued to this gentleman."

Random House books taken for review by the censors include two about China, four about Nazi Germany, two on ballet and Baryshnikov, a history of Russia, a book called "Art and Revolution," and "My Country and the World" by Soviet human rights leader Andrei Sakharov.

At the same time, the censors passed George Orwell's savage political satire, "1984," which was banned two years ago. But they seized, as in 1977, his other famous denunciation of totalitarian rule, "Animal Farm."

The other American book reported to have been taken came from the Random House group. It is called "The System of Freedom of Expression." No one knows yet whether it will be returned.