PERHAPS, as the promoters are no doubt praying, elaborate preparations to celebrate the 100th anniversary of the Statue of Liberty will whip up their own momentum and triumph over the general inertia that is traditional during the summer doldrums. That strategy, plus the fact that the competition on the other networks consists entirely of reruns, might win respectable ratings for ''Liberty,'' a Robert Greenwald production being unveiled on Channel 4 at 8 this evening. But no amount of hoopla and bluster can turn this three-hour television movie into anything more than an old-fashioned fizzle.
There were evidently a number of off-camera hitches. The script was written by Pete Hamill, the columnist and author, who now, reportedly dissatisfied with the production, prefers the use of the pseudonymous ''Robert Malloy'' in the screen credits. As an Irish-American in good standing, Mr. Hamill's normal writing style blends belligerent sentimentalilty with insightful toughness. ''Liberty'' has sentimentality to spare, most notably in its warmhearted ''melting pot'' depictions of the immigrant experience. But, except for some passing snippets about patriotism, glory and national strength often being the last refuges of scoundrels, there is no toughness, no hard edge here. This is standard uplift formula.
Mixing dollops of fact with enormous chunks of fiction, the story begins in 1869. Arriving in New York harbor is Jack Marchand (Chris Sarandon), a Jewish coppersmith from France, who will finally find work in the shop of gregarious, generous Seamus Reilly (George Kennedy), an Irishman whose top assistant is Robert Johnson (LeVar Burton), a recently freed black slave. Meanwhile, in Paris, Frederic Auguste Bartholdi (Frank Langella), the sculptor, is dining with the wealthy and influential Pierre Laboulaye (Jean-Pierre Cassel). After observing that ''Flaubert is right - art is the only answer,'' Mr. Bartholdi reveals his idea for a statue, made in France, that will celebrate liberty even as Louis Napoleon goes about trying to pick a war with Prussia.
The stage is thus set and the generally competent performers, directed by Richard Sarafian, proceed to go through the rather uninspired motions that will end, as we reasonably suspect, with the 1886 unveiling on Bedloe's Island of ''Liberty Enlightening the World.'' It was the practical politician William Marcy (Boss) Tweed, we learn, who suggested that the mammoth sculpture be called the Statue of Liberty, the better to fit into newspaper headlines.
The aristocratic Mr. Bartholdi, in addition to his incessant lobbying to get his unusual project financed and completed, is also torn between the demands of his fiercely possessive mother (Claire Bloom) and his understandably puzzled mistress (Corinne Touzet). On the New York side of the ledger, Jack Marchand is laboring under the burden of becoming the perfect immigrant. He marries an illiterate Irish Catholic named Moya (Dana Delany), who is determined to learn all about Beethoven and Rembrandt in order to please her moody husband. He falls in love with a wealthy and learned New York poet named Emma Lazarus (Carrie Fisher), who is also Jewish, and opens her eyes to the poor people around her. His best friends are an Irishman and his black co-worker, and he will end up as an invaluable assistant to the demanding Mr. Bartholdi. The immigrant experience has never been so smoothly enlightened. That is the problem with ''Liberty.''
There are intriguing details scattered along the way. Mr. Hamill clearly is taken with the story of Mr. Bartholdi being approached by a potential American supporter, a successful producer of castor oil, insisting that the statue celebrate not freedom but eternal vigilance, and that the woman not carry a torch but wave a rifle. But it is precisely this kind of pointed anecdote that makes the rest of the dramatization seem so pedestrian.