Denmark is a close American ally deserving of far better from President Trump. The American people, who expect their president will put U.S. interests before his own ego, also deserve better.

I say this in light of insults Trump directed at the Danish prime minister on Wednesday after she labeled his efforts to buy Greenland as "absurd." Trump's outburst follows his similarly petulant tweet on Tuesday that "based on Prime Minister Mette Frederiksen’s comments, that she would have no interest in discussing the purchase of Greenland, I will be postponing our meeting scheduled in two weeks for another time."

Trump might whine about Frederiksen's language, but considering the Danish political furor that Trump's Greenland flippancy produced, her response was understandable. He should have let it pass. Instead, Trump has wrecked a two-day September visit to Denmark for which, Frederiksen noted, "preparations were well under way." The logistical complexities of a presidential visit are huge.

Denmark's frustration is understandable, and Trump's disrespect to Denmark is both idiotic and immoral.

Idiotic, because Denmark is a committed and capable ally. The Danish military is well-trained and supported by increasingly advanced capabilities. Danish maneuver infantry, air strike, cyber, and anti-ship forces are especially impressive. They attest to a nation that intends to fight alongside keystone NATO forces if Russia ever attacks the alliance. The same cannot be said of many other European powers, including Belgium, Germany, and perhaps soon, Italy. But Trump's words will only spark Danish public anger and empower left-wing politicians who want to weaken our alliance. The stakes here are potentially great. What, for example, if Denmark now chucks the U.S. military out of Greenland? That would greatly reduce our ability to detect and defend against Chinese and Russian nuclear attacks.

Trump's words are also immoral.

Unlike many U.S. allies, Denmark has fought alongside us in both Afghanistan and Iraq. Seven Danes gave their lives in Iraq. In Afghanistan, 43 Danes died, and hundreds more were wounded. There, Denmark chose to operate in the restive Helmand Province, taking the fight to the enemy. We should thank Danes for giving their sons' and daughters' lives for our common cause.

The president swore an oath to uphold American interests. His gratuitously harsh words toward Denmark do the exact opposite.