WASHINGTON, Jan 20 (Reuters) - The United States said on Friday it was appealing a World Trade Organization ruling in a dispute with Mexico over labels to assure consumers the tuna they buy at the grocery store was not caught through methods that hurt dolphins.

"Our dolphin-safe labeling measures for tuna products provide information for American consumers as they make food purchasing decisions for their families," Andrea Mead, a spokeswoman for the U.S. Trade Representative, said.

Mexico has complained for years that U.S. dolphin-safe rules unfairly discriminate against its tuna exports and challenged the labeling provisions at the WTO in 2008.

A WTO panel ruled in September that U.S. regulations did not discriminate against Mexico, but said they were more restrictive than they needed to be to meet the goals of informing consumers and protecting dolphins.

Under the United States' dolphin-safe labeling provisions, producers of tuna products - whether foreign or domestic - have the option of labeling tuna products that meet the standards of the U.S. provisions as dolphin safe, USTR said.

One such condition, challenged by Mexico, is that the label cannot be used if dolphins are purposefully chased and encircled in order to catch tuna. Some Mexican fishing vessels use this method when fishing for tuna.

U.S. consumer rights group Public Citizen commended the Obama administration for appealing the ruling.

It said the labels allow consumers to "vote with their dollars" for dolphin-safe methods.

The United States has argued the matter should be addressed through dispute settlement proceedings of the North American Free Trade Agreement, rather than the WTO.

However, Mexico has preferred to go through the Geneva-based world trade body.

If the United States loses the appeal, it could be required to amend its dolphin-safe labelling laws or face possible Mexican trade sanctions.

(Reporting by Doug Palmer)

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