You can’t fire me. I quit!

The U.S. ambassador to Estonia is resigning in protest over President Trump’s critical statements about NATO. And the commander-in-chief may have even more criticism of the North Atlantic alliance to utter when he travels to Europe next week.

James D. Melville Jr., a career diplomat who’s represented the U.S. in the Baltic nation of Estonia since late 2015 (appointed by Barack Obama), will retire at the end of this month. On Facebook, he wrote:

The honorable course is to resign. Having served under six presidents and 11 secretaries of state, I never really thought it would reach that point for me….

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.

Lead by the U.S., th69-year-old alliance was the unifying, protective bulwark of the struggle against Communism and Moscow for decades. Since the collapse of the Soviet Union in 1991, several former Soviet states, including Estonia, have joined NATO. And NATO has also played a prominent role in the Afghanistan fighting.

All of which annoys Russian President Vladimir Putin, who’s ordered military maneuvers and air thrusts over and near the Baltic states, where U.S. troops are also stationed.

And he’s sought to weaken NATO ties through energy deals and, in NATO member Turkey, large sales of military hardware that is not compatible with other members. Putin’s military moves into Georgia and Crimea make the smaller Baltic countries even more nervous about NATO’s willingness to prevent a Russian grab of them.

While perhaps justified on a fiscal basis, Trump’s blunt criticism of NATO countries for not fully fulfilling their previous pledges of spending two percent of GDP on defense, has made Europe nervous about the New Yorker’s commitment to the vital alliance.

While previous presidents have complained about NATO defense spending, none did so as harshly as Trump, who pronounced the alliance “obsolete” before the 2016 election.

Subsequent administration reassurances have not quelled Euroope’s worries, which are existential for them, not just geopolitical games.

Adding to their concerns is Trump’s oft-repeated desire for improved relations with Moscow, which by itself is not unprecedented for American chief executives. But now Trump has scheduled a mid-month summit with Putin in Finland after he criticizes whatever he’s going to criticize to NATO in Brussels.