By David Alire Garcia

MEXICO CITY (Reuters) - A group of former U.S. ambassadors to Mexico representing both Republican and Democratic presidents have banded together to urge President Donald Trump to treat trade and migration as separate issues, the diplomats wrote in an article.

The article is signed by all six living ex-U.S. ambassadors to Mexico who spanned the presidencies of George H.W. Bush in the late 1980s to Barack Obama, and comes as Mexican officials are negotiating a potential deal in Washington this week before Trump's threatened tariffs take effect on June 10.

"We urge these senior leaders to delink trade and immigration and find ways ahead to address the real problems around Central American migration," the diplomats wrote in a copy of the article reviewed by Reuters and set to be published later on Wednesday. "Otherwise, we face lose-lose outcomes."

Frustrated by the volume of migrants arriving at the United States' shared border with Mexico, Trump last week said he would impose tariffs on Mexican imports later this month.

The president threatened to start the tariffs at 5% and increase them to as much as 25% later this year if the Mexican government does not do more to curb migration.

The planned tariffs have drawn criticism from Mexican officials as well as business and industry groups on both sides of the border, who have warned of increased costs for U.S. companies and consumers.

The former ambassadors joined that chorus, arguing that the economic blow would make it harder for Mexico to marshal the resources necessary to manage migration, invest in Central America and pursue other shared priorities.

By straining the binational relationship, the tariffs could also stymie efforts to fight cross-border crime, the group wrote.

"Progress will be more difficult if the U.S. is perceived to harm Mexican jobs with tariffs," the article said.

The group also raised concerns about what the tariffs would mean for a deal struck last year between the United States, Mexico and Canada to replace the North American Free Trade Agreement (NAFTA).

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The Trump administration is seeking congressional approval of the pact, known as the United States-Mexico-Canada Agreement.

U.S. businesses and consumers would pay a steep price for the tariffs, not to mention any potential retaliatory measures from Mexico, the diplomats said.

"If the U.S. imposes new tariffs, expect the same from Mexico on U.S. agricultural products that will have little chance of finding new markets quickly," the group wrote.





(Reporting by David Alire Garcia; writing by David Alire Garcia and Julia Love; editing by Darren Schuettler)