Mexican President Andrés Manuel López Obrador blasted President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE’s decision to impose tariffs on exports from his country in response to an immigration crisis on the border, writing in a letter that Trump’s “America First” policy was a “fallacy.”

“With all due respect, although you have the right to express it, 'America First' is a fallacy because until the end of times, even beyond national borders, justice and universal fraternity will prevail,” López Obrador wrote in the two-page letter to Trump.

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The Mexican president said his country was doing “as much as possible” to stem the flow of Central American migrants through his country to the United States, and “without violating human rights.”

He also wrote that Mexico wanted to avoid a confrontation with the United States on the issue.

Trump in a tweet on Thursday announced he was imposing a 5 percent tariff beginning June 10 on all Mexican imports “until such time as illegal migrants coming through Mexico, and into our Country, STOP.”

The White House released a statement saying the tariff would increase by 5 percent each month until it reaches 25 percent.

It’s unclear how the administration will measure Mexican progress on stemming migration.

Administration officials on a call Thursday did not establish a benchmark. Acting White House chief of staff Mick Mulvaney Mick MulvaneyOn The Money: House panel pulls Powell into partisan battles | New York considers hiking taxes on the rich | Treasury: Trump's payroll tax deferral won't hurt Social Security Blockchain trade group names Mick Mulvaney to board Mick Mulvaney to start hedge fund MORE said progress would be measured on an "ad hoc" basis and would be monitored “day-by-day and week-to-week.”



López Obrador announced in his letter that Foreign Secretary Marcelo Ebrard will head to Washington on Friday in pursuit of a deal. Ebrard was scheduled to visit Washington in mid-June to meet with congressional and administration leaders.



He also urged Trump to move away from the tariffs, stating that “social issues are not resolved through taxes or coercive means.”