"The best I've ever had," said Gian Carlo Menotti at a press conference yesterday, in describing the performance of his opera "The Consul" at the Spoleto Festival U.S.A here, which he himself established and heads.

Not having seen "The Consul" on stage before, I can't make comparisons with previous versions. But on its own terms, the production premiered Thursday night at the Gaillard Municipal Auditorium seemed as taut and compelling as one could wish for under any circumstances.

"The Consul" gave clear proof that Spoleto U.S.A. can muster the same high standards as its Italian counterpart, the 20-year-old Festival of Two Worlds.

Meanwhile, as word of the attractions of the Charleston event continues to spread, ticket sales have been steadily mounting, and forecasts of a second-week sell-out are now making the rounds.

"The Consul" is a melodrama about European political outcasts of the '40s who are seeking asylum abroad, but who find themselves trapped in the coils of an indifferent bureaucracy.Magda Sorel, the heroine, tries to find refuge for herself and her infant, and hopes for reunion with her renegade husband, who's in hiding from the secret police. But between her and the unseen consul barricaded behind an office door, lies a fatal maze of papers, formalities and delays. By the time help seems on the point of arrival, it's too late - the inevitable tragedy has been consummated.

Menotti's own libretto provided him with an ideal theatrical skeleton for his considerable lyric and dramatic gifts. There's nothing profound about the work- it's sentimentalized verismo, not for away from soap opera. But it's so perfectly realized that it is as touching and effective today as it was at its premiere in 1950.

The production had the same cohesiveness and sureness of touch as the opera itself. It had the benefit, for one thing, of Menotti's own stage direction and there's no doubt about it - the man is a magician when it comes to theatrical impact. For another thing it was blessed with a flawless cast in Marvelee Cariaga, a rising young singer from the West Coast, possessed a dramatic soprano of tremendous amplitude and penetration, which she uses with unerring musical sensitivity. A large woman with a strong, handsome face, she commanded the stage absolutely as Magda, and bought down the house with each of her extended arias.

The rest of the cast was on the same plane of distinction. The voices weren't all equally outstanding but the performances - as fusions of musicianship, acting, stylistic sense and stage presence - assuredly were David Clatworthy, Fredda Rakusin, Vern Shinall, Sandra Walker, Bibiana Goldenthal and Jerold Siena were the most conspicuous among them, but the accolade belongs to all.

This goes as well for other aspects of the production, which each element reinforced the merits of every other, including the somberly expressive decor by Carey Wong, the trenchant accents of Thomas Skelton's lighting, and the posied musical direction by Christopher Keene.

The Festival's one major dramatic premiere, however - Simon Gray's "Molly" - proved rather a dud. A four-character play set in a small English village in 1930, it strikes one on first encounter as slick but empty. It's a bit like one might imagine a poor early sketch for "Lady Chatterly's Lover" to have been becomes a lethal weapon, a bottle of sleeping pills dim-witted gardener behind the back of her much older crochety and deaf husband. A loyal, spinsterish housekeeper makes up the complement.

The script doesn't just telegraph it punches, it sends up signal flares - a pair of garden shears which becomes a lethal weapon a bottle of sleeping pills downed in a single gulp. The whole thing has far more artifice than art, and little besides a few facile wise-cracks to recommend it.