PROSCIUTTO with melon. Prosciutto with figs. Prosciutto on a slice of crusty Tuscan bread. Prosciutto undulating gently across a platter, surrounded by cheese, salami, sausage and olives. Any or all of these combinations may figure in the fantasies of an American traveler just returned from sampling Italy's most famous pork product, a flavorful and somewhat chewy ham cured through a complicated, lengthy process of salting and air drying.

Our eager Italophile might head for the nearest deli or specialty food shop, determined to satisfy a craving for a slice of robust Parma prosciutto or for the more delicate flavor of the ham cured in San Daniele, not far from Venice.

Alas, the search will be fruitless, for the United States has banned the importation of Italian prosciutto and other cured pork products since 1978. The reason: An outbreak of African swine fever in Sardinia four years ago caused Italian pork to run afoul of U.S. Department of Agriculture regulations.

Though harmless to human beings, the swine fever virus is almost invariably lethal to hogs. No vaccines exist, and in Sardinia and other European regions plagued by outbreaks, hog producers have had to slaughter whole herds of swine to prevent further spread of the disease. The USDA's Veterinary Services Office, which administers the section of the Code of Federal Regulations aimed at preventing the entry of livestock diseases into this country, is particularly concerned because African swine fever has now surfaced in Brazil, the Dominican Republic and, most recently, Haiti. Officials think the disease made its way to the Western Hemisphere through contaminated pork products from Spain or Portugal, which were then consumed by garbage-browsing pigs in Central and South America.

The ban not only covers prosciutto, but all smoked or salt-cured Italian pork products. Most salami and sausages fall into this category, as does pancetta, Italy's lean and delectable bacon. Nor can mortadella, the well-known boiled sausage of Bologna, fall under American knives. Canned pork is exempted from the ban, but this is poor solace--even if Italians had the bad sense to can their hams, American epicures would be certain to disdain them.

Even before the 1978 embargo, Italian producers had to obtain special authorization to prepare and ship pork to the U.S. These restrictions were imposed during the early 1970s, following the appearance of swine vesicular disease and other maladies that continue to afflict Italian pigs. Still, imported prosciutto was entering the country in sizable quantities before the embargo. Now, even producers willing to meet strict requirements on the raising, butchering and processing of hogs cannot get approval to export their goods.

Anxious to end the ban, the Parma Ham Consortium has been lobbying the U.S. government, both directly and through the Italian Embassy in Washington. For centuries, Parma producers have prided themselves on the excellence of their cured hams, maintaining that the special quality of the province's air accounts for their superior flavor. Eager to export Parma prosciutto to a potentially lucrative American market, the producers argue that controls--not a total embargo--are the answer. According to the consortium, no contaminated animals could possibly be used in curing prosciutto for export, since the Italian government prohibits the transportation of hogs and pork products from Sardinia to other European countries, or even to other parts of Italy.

Moreover, footloose pigs can't simply drift over the forbidden borders. As Alberto Teodoli, agricultural attache for the Italian Embassy, points out, "Sardinia is an island and pigs don't swim" (especially when they are of the 300- to 400-pound dimensions used in making prosciutto).

USDA officials acknowledge that this reasoning has merit, but say their hands are tied because the regulations must be applied to political entities as a whole rather than to their geographic components.

The Italians say that even if the swine fever virus were present in their hogs, the curing process for prosciutto would destroy it. Taking this point seriously, the American government has just begun a series of experiments at Plum Island Animal Disease Center on Long Island, the only research laboratory in the country permitted to work directly with live viruses affecting swine.

The scientists have already located hogs of the same proportions as their Italian brethren. Next they will infect the animals with African swine fever and other diseases, butcher them and, employing a special humidity-controlled chamber supplied by the Italian government to simulate Parma's climate, cure the meat in the prescribed Italian manner. As an independent check, parallel experiments are under way in Brescia, Italy.

Similar tests on smoked and salt-cured salami and sausages have shown that the viruses can survive in the meat up to two years, says John Graves, associate director of the Plum Island facility. Nonetheless, the Italians are optimistic that prosciutto will prove its mettle.

About a year from now, once the experiments are completed, the two governments will probably publish their findings jointly. At this point, the USDA must examine the evidence and decide whether to leave the ban unchanged, to lift it altogether or to compromise by allowing importation with some restrictions. Even with the most favorable results, then, it's clear that the consumer impatient for a taste of imported prosciutto is in for a wait.

Meanwhile, domestically produced prosciutto is filling the display cases of American delicatessens and specialty food stores. Some consumers may even think they are buying imported prosciutto. One brand name, Daniele, can be easily confused with genuine San Daniele prosciutto from the Veneto region of Italy. Citterio, another brand widely available in Washington, is made in Pennsylvania by a subsidiary of an old Milan-based company. Established in 1973 in response to the first restrictions on imported prosciutto, Citterio initially built a market based on its name recognition among first- and second-generation Americans of Italian descent.

Is made-in-America prosciutto as good as the genuine article? Domestic producers say yes, pointing out that they employ Italian technicians to make sure the required procedures are followed as closely as possible, given federal regulations.

Controlling that more nebulous variable, the climate, is another matter. Citterio chose its processing site in the Poconos specifically because the clean, dry air in the surrounding hills resembled the renowned climate of Parma. However, anyone who has visited both the Poconos and Parma may be pardoned for entertaining a few doubts on the similarities between the two.

Armando Pasetti of the John Volpi Co., a small midwestern firm in business since 1902, admits that "St. Louis does not have the best climate for making prosciutto." But, he adds, "We have compressors that condition the air and humidity. And even in Parma, the hams you see hanging in the open air are just there to dry out for a day or two after having the salt washed off. Then they're put in the aging room, just as they are here."

Volpi prosciutto is, incidentally, not easy to find in Washington. Pasetti could name only one source, Viareggio Italian Delicatessen (3740 12th St. NE). And the day I called, the proprietor reported a single three-pound ham in stock, which she planned to sell in its entirety to be hand-cut and savored a bit at a time by some lucky customer.

Whether domestic prosciutto continues to dominate the market or is rejoined by Italian prosciutto, a taste for the product is beginning to take hold, particularly on the East and West coasts. "We see a growing appreciation for prosciutto," says Edward Sharp, vice president of Citterio. "Our primary customers used to be Italians who had recently arrived here, but now plenty of other people are buying it."

Pasetti agrees. Sales are up and the market is broadening as "people travel more, eat in Italian restaurants and get to know Italian food more and more."