Image copyright Reuters Image caption Greenland is an autonomous Danish territory between the North Atlantic and Arctic oceans

Greenland has said it is "not for sale" after President Donald Trump stated that he would like the US to buy the world's biggest island.

The president is said to have discussed the idea of purchasing Greenland, an autonomous Danish territory, during dinners and meetings with advisers.

But Greenland's government dismissed the idea, saying: "We're open for business, not for sale."

Mr Trump's plans have also been quickly dismissed by politicians in Denmark. "It must be an April Fool's Day joke...but totally out of [season]!", tweeted former Prime Minister Lars Lokke Rasmussen.

The Wall Street Journal (WSJ), which first reported the news, said Mr Trump had spoken about the purchase with "varying degrees of seriousness".

Sources quoted in other media differed over whether the president was joking or seriously hoping to expand US territory.

How has Greenland reacted?

Officials in Greenland have insisted that the island is not on the market.

"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. We're open for business, not for sale," the foreign ministry said in a statement shared on social media.

Greenland Premier Kim Kielsen repeated the comments in a separate statement. "Greenland is not for sale, but Greenland is open for trade and cooperation with other countries, including the USA," he said.

Greenland MP Aaja Chemnitz Larsen was also among those to dismiss the president's interest.

"No thanks to Trump buying Greenland!", she wrote on Twitter, adding that a "better and more equal partnership with Denmark" was the way forward.

Poul Krarup, editor-in-chief of Greenland's Sermitsiaq newspaper, told the BBC he "couldn't believe" Mr Trump's remarks.

"Greenland is an independent area in the Danish kingdom and must be respected as such," he said.

But he said he thought the chances of Mr Trump's reported ambitions being realised were unlikely.

"We'd like to cooperate with the US, no doubt about that, but we are independent and we decide who our friends are."

What about Denmark?

Politicians in Denmark have ridiculed the idea of a possible US acquisition.

"If he is truly contemplating this, then this is final proof, that he has gone mad," foreign affairs spokesman for the populist Danish People's Party, Soren Espersen, told national broadcaster DR.

"The thought of Denmark selling 50,000 citizens to the United States is completely ridiculous."

"Out of all things that are not going to happen, this is the most unlikely. Forget it," Danish Conservative MP Rasmus Jarlov wrote on Twitter.

Denmark's Prime Minister Mette Frederiksen, who took office earlier this year, has not commented on the reports.

She is set to visit Greenland this weekend and has said she is "very much looking forward" to it.

Mr Trump is scheduled to visit Denmark in September but there is no indication that the possible acquisition of Greenland is on the agenda.

The WSJ reported that it was "unclear" how the US would go about acquiring Greenland if Mr Trump was serious.

Where is Greenland?

Greenland is the largest island in the world (after Australia, which is defined as a continent in its own right). It is an autonomous Danish territory, located between the North Atlantic and Arctic oceans.

It has a population of about 56,000 people concentrated around the coastline. Almost 90% are indigenous Greenlandic Inuit people. It has a limited self-government and its own parliament.

More than 80% of the island is covered by an ice cap which is feared to be melting due to global warming.

The ice melt has increased access to the island's mineral resources.

But it's also believed that the receding ice may expose toxic nuclear waste that was left at several US military sites during the Cold War.

Why would it be appealing to Trump?

Mr Trump has reportedly taken an interest in Greenland, in part, because of its natural resources, such as coal, zinc, copper and iron ore.

But while Greenland might be rich in minerals, it currently relies on Denmark for two thirds of its budget revenue. It has high rates of suicide, alcoholism and unemployment.

Image copyright AFP Image caption Reports differ over whether Mr Trump was serious about trying to purchase Greenland

Two people briefed on the discussions told the New York Times the president was also interested in Greenland's "national security value" because of its location.

The US has long seen the island as being strategically important and established an air force and radar base there at the start of the Cold War.

Republican Representative Mike Gallagher described Mr Trump's idea as a "smart geopolitical move".

"The United States has a compelling strategic interest in Greenland, and this should absolutely be on the table," he tweeted.

Can countries buy territories?

Historically, countries have acquired territory not only through military conquest but also financial deals.

Under the 1803 Louisiana Purchase, the US acquired about 827,000 sq miles (2.1m sq km) of land from France for $15m (£12.3m). In 1867, the US reached a deal with Russia to purchase Alaska for $7.2m.

The US later purchased the Danish West Indies in 1917 and renamed them the US Virgin Islands.

However, Duke University law professor Joseph Blocher told the BBC that the practice "has basically dried up".

"I think in part because nations can often get what they want without expanding their sovereign territory, and also because... people can't just be bartered around like chattel anymore," said Professor Blocher.

"An outright sale would have to be approved by the United States, Denmark, and the people of Greenland, and the odds of that seem vanishingly small," he added.

Has the US ever tried to buy Greenland before?

The idea of purchasing Greenland was first mooted during the 1860s under the presidency of Andrew Johnson.

In 1867, a report by the US State Department suggested that Greenland's strategic location, along with its abundance of resources, made it an ideal acquisition.

But no official move was made until 1946, when Harry Truman offered Denmark $100m for the territory.

He had earlier toyed with the idea of swapping land in Alaska for strategic parts of Greenland, according to AP.