WASHINGTON – Greenland's government told President Donald Trump on Friday that the island was "not for sale" following reports the president entertained the idea of buying the Danish territory.

"We are open for business, but we’re not for sale,” wrote Greenland's Ministry of Foreign Affairs in a tweet

The Wall Street Journal first reported on Thursday that Trump had floated the idea of buying Greenland, an autonomous Danish territory, though it was unclear if Trump was joking or not, based on other reports. The Associated Press said Trump's interest in Greenland was characterized by "varying degrees of seriousness."

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The U.S. reportedly proposed buying Greenland from Denmark in 1946 for $100 million, the AP and the Journal both reported. The U.S. had maintained weather stations and military facilities on the island during World War II.

The U.S. currently maintains a large military base – Thule Air Base – in Greenland. It is the U.S. military's northernmost installation, as it is 750 miles north of the Arctic Circle.

Although Trump had reportedly taken an interest in the island's natural resources, Greenland's government took the opportunity to promote tourism.

"#Greenland is rich in valuable resources such as minerals, the purest water and ice, fish stocks, seafood, renewable energy and is a new frontier for adventure tourism," read the Greenland Ministry of Foreign Affairs tweet, including a link to the Greenland tourism website.

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Contributing: Rebecca Morin