Something is rotten in President Trump canceling his trip to Denmark.

In yet another example of Trump's undiplomatic rudeness, the bumptious billionaire has canceled an already scheduled state visit to Denmark, apparently upset that the tiny, friendly nation won’t jump at his command.

Invited to Copenhagen by Queen Margrethe II, Trump specifically had said that the visit was not dependent on Denmark’s level of interest in his idea of buying the vast island of Greenland from the Danes. Once both Danish premier Kim Kielsen and prime minister Mette Frederiksen said there is no chance of them selling Greenland, though, Trump gave the lie to his own earlier words by abruptly canceling the trip and specifically citing Greenland as the reason.

To say Trump’s behavior here is childish is to insult children. Or at least, the worst of spoiled brats now have a new role model.

Small though it is, Denmark is a valuable and longstanding ally. It allows the U.S. to operate the Thule Air Base on Greenland, which is of great strategic significance, on terms extremely generous to the U.S. Denmark stands with its larger ally when most other nations don’t, including in joining Operation Iraqi Freedom in 2003. Denmark has no obvious direct interest in the Middle East, but it provides troops when asked — 43 of whom have lost their lives in American-led missions in Iraq, Syria, and Afghanistan. (In terms of percentage of population, that would be the equivalent of U.S. losses of some 2,500 personnel.)

Trump’s idea of buying Greenland might well be mutually beneficial to Americans and Danes, but it obviously came out of proverbial left field as far as the Danes were concerned. Obviously, nobody in the Trump administration had bothered telling them of Trump’s interest. It would be unreasonable to expect them to immediately comply, or even to comply at all. Even if Denmark decides it makes sense to sell, there are the desires of Greenland’s 56,000 inhabitants to consider. Because this state visit was arranged without any signal that a purchase of Greenland was on the agenda, much less even being considered, it is a nasty trick indeed to kill the trip just because Denmark isn’t jumping at the chance to relinquish its largest territory.

Naturally and correctly, the people of Denmark and Greenland find Trump’s crude power play “deeply insulting,” in the words of former prime minister Helle Thorning-Schmidt. “Total chaos,” former finance minister Kristian Jensen wrote. “This has gone from a great opportunity for a strengthened dialogue between allies to a diplomatic crisis.” (Quotes from the New York Times.)

The rotten smell to all this is emanating not from the state of Denmark, but from the current state of the Oval Office. The president’s diplomatic hygiene is abominable.