The United States Department of Agriculture will relax a decades-long ban on the importation of many cured-pork products from some regions of Italy starting May 28, greatly increasing the number and variety of salumi in markets and restaurants here.

On Friday, the department’s Animal and Plant Health Inspection Services announced that an in-country assessment had determined that four regions and two provinces in Northern Italy are free of swine vesicular disease, a dangerous communicable ailment that infects pigs, and that “the importation of pork or pork products from these areas presents a low risk.”

Some pork importers and producers, in this country and in Italy, celebrated the changes, saying they would allow more Italian cured-pork products to make their way to American tables.

But others were unable to judge the ultimate impact of the ruling because the Inspection Services did not specify what standards would now have to be met by Italian producers, nor the expense of meeting them. Despite repeated requests, the agency did not immediately provide more details about its decision.