The U.S. Department of Agriculture has proposed a change in regulations that would relax restrictions on pork imports from certain areas of Mexico, potentially allowing for increased U.S. imports at a time of a supply shortage.

The proposal would permit pork to be imported from certain parts of Mexico defined as having a low risk of classical swine fever (CSF), the USDA's Animal and Plant Health Inspection Service (APHIS) said in a posting on Tuesday in the Federal Register.

CSF, also known as hog cholera, is a highly contagious viral disease of swine that was eradicated in the United States in 1978 after a 16-year campaign.

Swine typically cannot enter the United States from regions affected by CSF. The most common method of transmission is through direct contact between healthy swine and infected animals.

Under the proposal, pork and pork products would have to be derived from swine raised on farms meeting stringent sanitary and biosecurity requirements, and the facilities would be subject to periodic inspections by U.S. authorities.

The USDA said it would provide safeguards against commingling of products from the designated safe areas with those that do not meet the proposed requirements.

The APHIS currently recognizes nine Mexican states as free of CSF: Baja California, Baja California Sur, Campeche, Chihuahua, Nayarit, Quintana Roo, Sinaloa, Sonora and Yucatan.

The new rule would incorporate the additional states of Aguascalientes, Colima, Guanajuato, Jalisco, Michoacán, Querétaro, San Luis Potosí and Zacatecas into a zone showing a low risk for CSF, and from which exports could be allowed under certain conditions.

Mexico had petitioned the APHIS in 2007 to recognize the additional states as CSF-free in order to expand its export markets. Since then APHIS officials have completed a series of site visits and concluded that a low but manageable risk still exists.

The exception would be the state of Chiapas, where the USDA said the disease threat remained unacceptably high.

The public can comment on the proposal until Sept. 29.

The USDA said it did not expect any increase in supplies from Mexico to significantly affect U.S. markets.

The annual value of U.S. pork and pork product production averaged almost $15.9 billion from 2010 through 2012. The annual value of U.S. imports of pork and pork products from Mexico over the same period averaged about $31 million, or less than 0.3 percent of U.S. domestic supply.

The United States imported 15.755 million pounds of pork from Mexico last year, versus 16.879 million in 2012. From January to May of this year imports totaled 7.943 million pounds.

Even so, additional supplies from Mexico could somewhat alleviate a pork shortage in the United States following the death of more than 7 million piglets from a killer virus over the past year.

Live hog futures on Tuesday slipped more than 2 percent to their lowest since June 11.

The USDA last Friday forecast retail pork prices would rise 5.5 percent to 6.5 percent in 2014. Through June prices were up 10 percent.

For the entire proposal, see: ons-on-the-importation-of-fresh-pork-and-pork-products-from-a-re gion-in-mexico (Reporting by Ros Krasny, additional reporting by Theopolis Waters in Chicago; Editing by Eric Beech, Will Dunham and Jeffrey Benkoe)