U.S. President Donald Trump aggressively defended his plans to take over Greenland in a phone call with Danish Prime Minister Mette Frederiksen, the Financial Times (FT) reported on Jan. 24.

In the weeks leading up to his inauguration, Trump publicly floated the idea of a U.S. takeover of Greenland, Canada, and the Panama Canal. In comments to reporters on Jan. 7, he refused to rule out the possibility of using military force to seize Greenland, which he said the U.S. needs for "economic security."

In a 45-minute call that took place a few days before Trump's inauguration, Trump grew increasingly aggressive and confrontational when Frederiksen said Greenland was not for sale, senior European officials told FT.

"It was a cold shower," one official said. "Before, it was hard to take it seriously. But I do think it is serious, and potentially very dangerous."

Another official described the conversation as "horrendous."

Greenland is an autonomous territory of Denmark, a NATO member state and traditional U.S. ally. The Arctic island houses both Danish and U.S. military bases and has vast reserves of mineral wealth.

Frederiksen reportedly told Trump that Denmark was willing to deepen cooperation with the U.S. on military bases and mineral extraction, but these offers did not appease him.

"The intent was very clear. They want it. The Danes are now in crisis mode," one official said.

The White House has not commented on the call. The Danish prime minister's office said it did "not recognize the interpretation of the conversation given by anonymous sources."

Trump's expansionist ambitions and disregard for state sovereignty carry alarming implications, particularly for Ukraine as it fights to restore its territorial integrity amid Russia's ongoing invasion.

Security analyst Alexander Khara, director of the Center for Defense Strategies in Kyiv, told the Associated Press (AP) earlier in January that Trump's posturing on Greenland bears echoes of Russian President Vladimir Putin's comments about Crimea.

Russia illegally annexed and occupied Crimea, an autonomous Ukrainian republic, in 2014. The annexation was widely condemned by most U.N. member nations, including the U.S. Washington imposed sanctions on Russian officials involved in the occupation.

A U.S. invasion of Greenland would disrupt the NATO alliance and undermine the Western coalition defending Ukraine's sovereignty against Russian aggression.

"We're in a time of transition from the old system based on norms and principles, heading to more conflicts, more chaos, and more uncertainty," Khara said.

Russia has said it is monitoring developments regarding Trump and Greenland due to Moscow's own "strategic interests" in the Arctic region.