UPDATE 2-U.S. groups accuse Mexico of dumping subsidized sugar

(New throughout, adds details of petition, background on USDA sugar buying program)

WASHINGTON, March 28 (Reuters) - U.S. sugar cane and sugar beet groups on Friday asked federal authorities to investigate what they called "dumped and subsidized" imports of sugar from Mexico, according to a filing with the U.S. International Trade Commission.

"It is our intention to file countervailing duty and antidumping petitions against the Mexican sugar industry," said Phillip Hayes, a spokesman for the American Sugar Alliance, which represents U.S. producers.

The petitions filed with the ITC and the U.S. Department of Commerce allege that the Mexican industry has shipped sugar to the United States at dumping-level prices, and also has received subsidies from Mexican federal and state governments.

Those actions will cost U.S. sugar producers nearly $1 billion in net income in 2013/14, the filings contend.

"It is hard for U.S. farmers to succeed when a subsidized industry that is largely government-controlled is dumping its product," said Hayes.

Officials with Mexico's agricultural ministry and the Mexican Sugar Chamber, which represents most of the country's cane mills, did not immediately comment.

Mexico has the right to export sugar to the United States on a tariff-free and quota-free basis under the North American Free Trade Agreement.

"That does not give the Mexican industry the right to export its surplus to the U.S. market at dumped prices," the groups' petition said.

The U.S. Department of Agriculture estimates sugar imports from Mexico in 2013/14 at 1.745 million short tons, and in a preliminary forecast in February said shipments would jump in the 2014/15 marketing year to 2.26 million short tons.

USDA propped up the sugar market in 2013 buy purchasing excess supplies, which it then sold at a loss to ethanol producers and others. It has warned that similar action might be needed this year.

The groups urging ITC action included the American Sugar Cane League, American Sugarbeet Growers Association, American Sugar Refining Inc, Florida Sugar Cane League, Hawaiian Commercial and Sugar Company, Rio Grande Valley Sugar Growers, Inc, Sugar Cane Growers Cooperative of Florida, and the United States Beet Sugar Association.

(Additional reporting by Chris Prentice in New York; Editing by Susan Heavey, Jonathan Oatis and David Gregorio)