It was unclear why Trump might want the United States to buy Greenland.

President Donald Trump has pushed top aides to investigate whether the U.S. government can purchase the giant, ice-smothered island of Greenland, two people with direct knowledge of the directive said.

The presidential request has bewildered aides, some of whom continue to believe it isn't serious, but Trump has mentioned it for weeks. The two people with knowledge of the presidential demand spoke on the condition of anonymity because they weren't authorized to reveal such White House planning.

As with many of Trump's internal musings, aides are waiting for more direction before they decide how seriously they should look into it.

Among the things that have been discussed is whether it is even legal, what the process would be for acquiring an island that has its own government and population, and where the money to purchase a giant landmass would originate.

Trump's interest in acquiring Greenland was first reported by the Wall Street Journal.

According to the Central Intelligence Agency's World Factbook, Greenland is 2.2 million square kilometers, with 1.7 million of that covered in ice. It has considerable natural resources, such as coal and uranium, but only 0.6 percent of the land is used for agriculture. It has around 58,000 residents, making it one of the world's smallest countries by population.

It is a self-governing country that is part of the kingdom of Denmark. Trump is scheduled to visit Denmark in two weeks.

Trump has touted his career as a real estate developer during the 2016 presidential campaign and made clear that he has retained an eye for real estate opportunities during his tenure in the White House. For example, he has said that North Korea could build famous hotels and resorts along its oceanfront properties, even though many foreigners are afraid to visit the country out of fear for their lives.

Typically, Congress must appropriate money before the White House can use it, but Trump has shown a willingness to get around those restrictions.

It was unclear why Trump might want the United States to buy Greenland, though his administration has identified the Arctic as an area of growing importance to U.S. national security interests.

"This is America's moment to stand up as an Arctic nation," Secretary of State Mike Pompeo said in May during a speech in Finland. "The region has become an arena of global power and competition."

With melting ice making the region more accessible, the United States has been firm in trying to counter moves by Russia and China in the Arctic. China declared itself a "near-Arctic nation" last year and has defended its desire for a "Polar Silk Road" in which Chinese goods would be delivered by sea from Asia to Europe.

China recently sought to bankroll the construction of three airports in Greenland, drawing concern from then-defense secretary Jim Mattis and prompting the Pentagon to make the case to Denmark that it should fund the facilities itself rather than rely on Beijing.

"Countries should be wary of piling on monumental debt, particularly 'loan to own' projects, that undermines their freedom of political action and sovereign choices," a Pentagon official, Johnny Michael, said previously. "Beijing's lack of transparency in its polar research, expeditionary activities and approach to natural resource development is also of concern."

Trump's desire to buy Greenland wouldn't be the first time an American president broached the idea.

The U.S. military had a presence on Greenland during World War II as a means to protect the continent if Germany ever tried to attack. After the war, the Truman administration offered Denmark $100 million to buy Greenland, according to the academic tome "Exploring Greenland: Cold War Science and Technology on Ice."

Since then, the Danish people have been wary of the United States' continued use of Greenland. The land was critical territory during the Cold War because of its location halfway between the United States and northern Europe and its proximity to the former Soviet Union. The Pentagon built its northern-most military installation, Thule Air Base, on Greenland in 1951, as a means for missile defense.

"Exploring Greenland," co-written by academics from Denmark and the United States, says that the U.S. military's "extensive activities in northern Greenland" were seen by Danish citizens and some politicians as "a violation of their national sovereignty."

Some on Thursday responded to the news with incredulity; others, with support.

"This idea isn't as crazy as the headline makes it seem," Rep. Mike Gallagher, R-Wis., said in a tweet. "This a smart geopolitical move. The United States has a compelling strategic interest in Greenland, and this should absolutely be on the table."

Most, however, responded with mockery.

Rep. Steve Cohen, D-Tenn., shared a news story about Trump's idea and mused: "A Great place for his 'presidential' library."

And Jonah Goldberg, a fellow at the American Enterprise Institute, tweeted that MAGA - the acronym for Trump's "Make America Great Again" campaign slogan - is "an anagram of Make Greenland American Already."