President-elect Donald Trump has reiterated his desire for the US to acquire Greenland and the Panama Canal, calling both critical to American national security.

Asked if he would rule out using military or economic force in order to take over the autonomous Danish territory or the Canal, he responded: "No, I can't assure you on either of those two.

"But I can say this, we need them for economic security," he told reporters during a wide-ranging news conference at his Mar-a-Lago estate in Florida.

Both Denmark and Panama have rejected any suggestion that they would give up territory.

Trump also vowed to use "economic force" when asked if he would attempt to annex Canada and called their shared border an "artificially drawn line".

The boundary is the world's longest between two countries and it was established in treaties dating back to the founding of the US in the late 1700s.

The president-elect said the US spends billions of dollars protecting Canada, and he criticised imports of Canadian cars, lumber and dairy products.

"They should be a state," he told reporters.

But outgoing Canadian Prime Minister Justin Trudeau said there isn't "a snowball's chance in hell" of the two countries merging.

Trump's news conference - less than two weeks before he is sworn in for a second term - was initially billed as an economic announcement to unveil a $20bn (£16bn) investment from Dubai developer Damac Properties to build data centres in the US.

But in a free-wheeling appearance, the president-elect went on to criticise environmental regulations, the US election system, the various legal cases against him, and President Joe Biden.

Among other things, he suggested renaming the Gulf of Mexico the "Gulf of America" and restated his opposition to wind power, saying wind turbines are "driving the whales crazy".

His remarks came as his son, Donald Trump Jr, visited Greenland.

Before arriving by private jet in the capital Nuuk, Trump Jr said he was going on a "personal day trip" to talk to people, and had no meetings planned with government officials.

When asked about Trump Jr's visit to Greenland, Danish Prime Minister Mette Frederiksen told Danish TV that "Greenland belongs to the Greenlanders" and that only the local population could determine its future.

She said "Greenland is not for sale", but stressed Denmark needed close co-operation with the US, a Nato ally.

Greenland - which has a population of just 57,000 - is the world's largest island and is a strategically important part of the Arctic region.

It has wide-ranging autonomy, but its economy is largely dependent on subsidies from Copenhagen and it remains part of the kingdom of Denmark.

Greenland is also home to a large American space facility and has some of the largest deposits of rare earth minerals, which are crucial in the manufacture of batteries and high-tech devices.

Trump suggested the island is crucial to military efforts to track Chinese and Russian ships, which he said are "all over the place".

"I'm talking about protecting the free world," he told reporters.

Since winning re-election Trump has repeatedly returned to the idea of US territorial expansion - including taking back the Panama Canal.

During the news conference, Trump said the canal "is vital to our country" and claimed "it's being operated by China".

He previously accused Panama of overcharging US ships to use the waterway, which connects the Atlantic and Pacific oceans.

Panamanian President José Raúl Mulino has rejected Trump's claims and said there is "absolutely no Chinese interference" in the canal.

A Hong Kong-based company, CK Hutchison Holdings, manages two ports at the canal's entrances.

The canal was built in the early 1900s and the US maintained control over the canal zone until 1977, when treaties negotiated under President Jimmy Carter gradually ceded the land back to Panama.

"Giving the Panama Canal to Panama was a very big mistake," Trump said. "Look, [Carter] was a good man... But that was a big mistake."

It's unclear how serious the president-elect is about adding to the territory of the US, particularly when it comes to Canada, a country of 41 million people and the second-largest nation by area in the world.

During the news conference, Trump also repeated a number of falsehoods and odd conspiracy theories, including suggesting that Hezbollah, the Islamist militant group, was involved in the US Capitol riot of 2021.