GENEVA/MEXICO CITY (Reuters) - Mexico’s economy ministry said on Thursday that it would appeal the World Trade Organization’s ruling against its challenge to U.S. tuna marketing rules, reigniting a long-standing dispute between major trade partners amid tough talks to update NAFTA.

“Mexico does not agree with the legal reasoning of the WTO ruling,” the ministry said in a statement after the decision, which undermines its claim for sanctions against Washington.

The ruling comes as Mexico, the United States and Canada engage in fraught talks to try to save the North American Free Trade Agreement, a lynchpin of the Mexican economy.

U.S. President Donald Trump says NAFTA is unfairly balanced in Mexico’s favor, killing U.S jobs and manufacturing, and has threatened to pull out of the pact.

U.S. Trade Representative Robert Lighthizer welcomed Thursday’s ruling, saying the WTO had now decisively rejected Mexico’s argument.

“I am pleased that WTO panels have finally agreed with the overwhelming evidence that U.S. dolphin-safe labeling requirements are accurate and fair,” Lighthizer said in a statement.

“The Trump Administration is committed to defending U.S. rights to enforce environmental measures that protect wildlife and facilitate fair trade.”

Mexico has said since 2008 that U.S. “dolphin-safe” labeling on tuna products is inconsistent with WTO rules and unfairly penalized its fishing industry. The United States has objected to Mexican fleets’ method of catching tuna that involves chasing and capturing dolphins in nets.

WTO judges had previously faulted the U.S. rules on tuna and authorized Mexican trade sanctions.

The United States, however, said it had done enough to bring its laws into line and claimed an exemption from the WTO rules on the grounds of environmental conservation.

Mexico has said it had cut dolphin deaths to minimal levels but that U.S. demands for paperwork and sometimes government observers were discriminatory. Tuna catches from other regions did not face the same stringent tests, the nation said.