The U.S. ambassador to Estonia has resigned over his frustration with 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 comments about the European Union (EU) and treatment of long-standing European allies.

In a private Facebook post first reported by Foreign Policy magazine, James Melville slammed Trump's recent comments accusing the EU of being set up to take advantage of the U.S., saying the remarks ultimately pushed him to resign.

ADVERTISEMENT

“For the President to say the EU was ‘set up to take advantage of the United States, to attack our piggy bank,’ or that ‘NATO is as bad as NAFTA’ is not only factually wrong, but proves to me that it’s time to go,” he wrote in the post, according to Foreign Policy.

“I leave willingly and with deep gratitude for being able to serve my nation with integrity for many years, and with great confidence that America, which is and has always been, great, will someday return to being right,” Melville added.

Melville is a senior U.S. diplomat who has served as ambassador to Estonia since 2015 and in various diplomatic roles for more than three decades. A top agency official told Foreign Policy that Melville's resignation was a major blow to the agency and a sign of significant resistance to Trump's policies among the diplomatic community.

“It means a lot when someone whose had it all in their career just says, ‘I can’t do this any longer,’” the unnamed official told Foreign Policy. “I just wonder who’s next.”

Melville's resignation comes just a day after it was reported that Trump urged French President Emmanuel Macron to withdraw France from the EU, suggesting that the U.S. would pursue a bilateral trade deal with his country if Macron pulled France from the trade bloc.

The Trump administration angered European allies, as well as Canada and Mexico, earlier this year by implementing tariffs on steel and aluminum, provoking retaliatory measures from several nations.