Until a more imposing and instructive fiasco makes its appearance, Bernardo Bertolucci's "1900," now at the K-B Fine Arts, can serve as the classic modern example of how a talented filmmaker's pretensions and compulsions may lead him into taking false positions on several fronts. In Bertolucci's case the self-deception seems to have encompassed his roles as artist, propagandist and promoter.

"1900" - a more accurate translation of the Italian title, "Novecento," would be "The 1900s" - was conceived as a pastoral-ideological epic about the triumphant ascent of socialism and the persistence of peasant culture and virtue in Emilia, the agricultural province of Northern Italy where Bertolucci was born. From the outset grandiose contradictions were built into this fundamentally regional epic, interweaving the lives of two characters, the high-born Alfredo Berlinghieri and the low-born Olmo Dalco, born on the Berlinghieri estate on the same day, April 25, 1900.

Bertolucci envisioned a mass international audience for his Emilian saga, so the conception was always distanced and romaticized by the requirements of a multi-million-dollar budget and an all-star cast drawn from the United States and France as well as Italy. In terms of language the film never had a national identity, and Bertolucci never intended to use live sound because he felt it might inhibit his muse during both the shooting and dubbing stages.

Americans are thrown by the English-language soundtrack, which does clash with the settings and reproduce lots of dead sound studio air and retain such oddities as socialist anthems actually being sung in Italian by Emilian extras. "1900" runs a shade over four hours, however, not counting the intermission - and somewhere along the way you cease to care whether it's in Italian, English, French, Japanese or pig Latin. In a self-defeating way Bertolucci has transcended his sound and language incongruities. Far from being triumphabtly seductive or compelling, his conception remains so diffuse, simplistic and dramatically unsatisfying that the language the actors speak in becomes a subordinate source of disillusion.

One doubts if a filmmaker as solemnly introvered as Bertolucci ever had a prayer of sustaining a popular epic narrative in the traditions of D.W. Griffith, Sergei Eisenstein and David O. Selznick. The remote possibility evaporates once the crusty old patriarchs embodied by Burt Lancaster and Sterling Hayden pass on and the boyish Olmo and Alfredo are promoted to young manhood, in the persons of Gerard Depardieu and Robert De Niro, respectively.

The most appealing performer happens to be Roberto Maccanti, who plays Olmo as a boy. The image of this lean, intent, fearless child, his tattered hat wriggling with frogs he has just caught and pinned beneath his hatband, imparts a mythic charm and promise that are never matched by subsequent effects or events. Obliged to imagine a history for the mature Olmo, Bertolucci seems to lose even his powers of visual invention. The character becomes a stolid symbol of moral strength, but that virtue is an arbitrary as the moral weakness ascribed to De Niro's Alfredo - and far less diverting to watch.

Bertolucci acts sanctimonious about sturdy Olmo and his fiancee, a dedicated Communist schoolteacher played by Stefania Sandrelli, but he hasn't the faintest idea of how to dramatize their relationship or illustrate their alleged superiority. If such idealizations don't bore him, they certainly mystify him. Seeking relief from this self-inflicted dose of virtue, Bertolucci follows De Niro to the sinful city, where he discovers a slinky, fashionably decadent galmor girl named Ada, impersonated by Dominique Sanda, and the movie itself shows some idly amusing signs of life.

At the intermission one has abandoned the idea of ever following an epic narrative, whether political or romantic in nature. You entertain the hope that "1900" might evolve into a spicier show now that naughty Ada has entered with her hedonistic lifestyle. No such luck. After a brief giddy interlude in which De Niro gets to ad-lib some funny business while supposedly high on cocaine, the plot summons him back to family responsibility and the picture begins to degenerate with a vengeance.

The agents - or dupes - of this degeneration are Donald Sutherland and Laura Betti, cast as Alfredo's overseer, Attila, and embittered cousin, Regina. These characters, who become a conspiratorial husband-and-wife monster team, sustain the rest of the movie on atrocities, which Bertolucci lamely ascribes to their fascist sentiments. It's abundantly and disreputably clear, however that Bertolucci rather than Alfredo relies on the cruelties of the villains. The reliance goes beyond storytelling desperation. Despite the espousal of wholesome Communist peasant virtue, it is vice that really attracts Bertolucci and inflames his filmmaking imagination.

"If "1900" begins with contradictions that can be excused as technicalities, it eventually flounders on contradictions that strike at the avowed motives of the filmmaker, who seems to have kidded himself about the sort of carrying-on that genuinely fascinate him and release his considerable pictorial and atmospheric talents.

"1900" is never unified dramatically, esthetic: Bertolucci's love of filmmaking for its own sake. When he appeared at the Eisenhower Theater following a preview of "1900," Bertolucci described it as "a movie about my love for cinema." Obviously, this is a line-of-last-defense position, necessitated by the movie's failure to live up to its original socio-political pretensions and by the filmmaker's grudging acquiescence to cuts requested by the distributors.

Nevertheless, it's a defensible position, unlike the one Bertolucci tried to defend when he envisioned bigger things for his creation and balked at cutting the film beyond 5 1/2 hours. "I like to shoot the movie," he said at the Eisenhower, "and comes a moment when producers say finish, but I don't want to finish."

"It's this kind of self-indulgence, which tempts every exceptional filmmaker, that has undermined "1900" in the long run. In his eagerness to reach everybody, Bertolucci has let his most ambitions project get so far out of hand that it's unlikely to attract anyone but confirmed movie nuts.