A cargo ship traverses the Agua Clara Locks of the Panama Canal in Colon, Panama. (AP: File)
US President Donald Trump has vowed to "take back" the Panama Canal in his inauguration speech, alleging the vital trade route is under China's control.
Doubling down on his pre-inauguration threat to reimpose US control over the canal, Mr Trump on Monday accused Panama of breaking the promises it made for the final transfer of the strategic waterway in 1999.
These are claims Panama has strongly denied.
Mr Trump has also taken issue with the "exorbitant" rates that the US government, navy and businesses have been charged to use the canal.
"We didn't give it to China. We gave it to Panama, and we're taking it back," Mr Trump said just minutes after being sworn in for a second four-year term.
This isn't the first time the US president has made it known he wishes to gain control over other territories or rename them.
So is it possible to do so, and why is Trump threatening it?
What is the Panama Canal?
The Panama Canal is a lock-type canal owned and administered by the Republic of Panama.
It connects the Atlantic and Pacific oceans through the narrow Isthmus of Panama.
The length of the Panama Canal from shoreline to shoreline is 65 kilometres and from deep water in the Atlantic (more specifically, the Caribbean Sea) to deep water in the Pacific about 82km.
The canal, which was completed in August 1914, is one of the two most strategic artificial waterways in the world — the other being the Suez Canal.
Ships sailing between the east and west coasts of the United States, which otherwise would be obliged to round Cape Horn in South America, shorten their voyage by about 15,000km by using the canal.
Who owns and controls the Panama Canal?
Since 1999, the government of Panama has had full authority and control of the waterway.
The US largely built the canal and administered territory surrounding the passage for decades.
Over the course of the 20th century, US control of the waterway was a point of contention for Panamanians, who believed that the country should have control of the passage.
On Jan 9, 1964, students protested in the then-US controlled canal zone over not being allowed to fly Panama's flag at a secondary school there.
The protests expanded to general opposition to the US presence in Panama.
US troops got involved and 28 people were killed. It is now commemorated in Panama as Martyrs' Day.
In 1977, the US and Panama signed a pair of accords that paved the way for the canal's return to full Panamanian control.
The US handed it over in 1999 after a period of joint administration.
In December 1989, the US invaded Panama in what was called Operation Just Cause to remove the country's dictator General Manuel Noriega.
The invasion resulted in his capture and extradition to the US to face charges of money laundering and drug trafficking.
This followed a decade of relations between the two nations becoming increasingly strained.
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Why have fees increased in the Panama Canal?
Fees for ships using the passage are set by the Panama Canal Authority.
Rates have soared in recent years due to drought in the area.
In 2023, rainfall fell by 30 to 50 per cent in Panama and the waterway began to dry up.
In response, the government reduced maximum ship weights and daily ship crossings in a bid to conserve the canal's water.
Congestion was eased in 2024 when the authority allowed rising numbers of ships to use the canal but it also increased charges and introduced some additional fees on January 1 this year.
The president of Panama said the prices were not inflated but Mr Trump disagreed.
Why is Trump saying China has influence over Panama?
China does not own the Panama Canal.
However, a Hong Kong-based corporation has run two of the canal's ports, located on the Caribbean and Pacific entrances, since 1997.
The company, part of Hutchison Ports, a subsidiary of Hong Kong-based conglomerate CK Hutchison Holdings, operates the ports of Balboa and Cristobal on either end of the canal.
In response to the accusations, the Panamanian comptroller's office that oversees public entities has announced "an exhaustive audit" would be launched "aimed at ensuring the efficient and transparent use of public resources" at the Panama Ports Company.
The comptroller's office said the aim was to determine whether the company was complying with its concession agreements, including adequate reporting of income, payments and contributions to the state.
Panama's President Jose Raul Mulino has denied that any other nation was interfering in the canal, which he said was operated on a principle of neutrality.
Could Donald Trump even take over the Panama Canal?
It's not clear how Mr Trump would seek to regain control over the canal, and he would have no recourse under international law if he decided to make a play for the passage.
Trump threatens to retake control of Panama Canal
Photo shows A container ship on a canal
US Think Tank, the Atlantic Council, suggests one way the US could regain some control over the canal is through investment.
"One option is to ramp up US investment in the canal and in the many businesses that directly and indirectly support canal operations," the organisation's Jason Marczak wrote in an article published on its website.
"The new Panamanian government is more pro-US than its predecessors.
"Mulino, who took office in July 2024, has made great efforts to more closely align Panamanian policy with US positions and is a ready partner to accelerate US investment in Panama. Recently, in Panama, I saw and heard concerns about a disproportionate uptick in Chinese investment and a yearning for more US companies to invest in Panama, from its tech sector to its maritime industry," he said.
There is evidence that Mr Trump has long-held beliefs that the US was "ripped off" when it gave control back to Panama.
According to think-tank the Atlantic Council, Mr Trump's Interactions with Panama came to a head in 2018 when a legal dispute arose between the Trump Organization and a Miami-based hotel investor, who was trying to break off ties with the Trump business.
The situation escalated into a stand-off with Panamanian authorities, and eventually, Mr Trump's name was taken off the hotel at the centre of the dispute.
What has Panama's reaction been?
Panama has also alerted the United Nations, in a letter seen by Reuters, to Mr Trump's remarks.
Mr Mulino has rejected Mr Trump's words, saying there is "no presence of any nation in the world that interferes with our administration".
Panama's UN Ambassador Eloy Alfaro de Alba noted that under the founding UN Charter, countries "shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state".
Gulf of Mexico Executive order
Can Trump rename the Gulf of Mexico?
Photo shows Donald Trump signs a page as a number of people stand around him
Mr Trump also vowed to change the name of the Gulf of Mexico to the Gulf of America.
Not long after being sworn in, he signed an executive order calling for the Gulf of Mexico to be renamed.
Mr Trump can do this, but only domestically.
The executive order only changes how the US refers to the basin, but that doesn't mean the rest of the world has to follow suit.
More talk of territorial expansion
In December, Mr Trump repeatedly mused about turning Canada into a US state, though it is unclear how serious he is about the matter.
On Monday, he again expressed interest in gaining control over Greenland, an autonomous territory of Denmark, saying the US needs to control it to ensure international security.
He made the comments while signing executive orders in the Oval Office of the White House on the first day of his second term as president.
He hasn't ruled out using military or economic power to persuade Denmark to hand it over.
Greenland's Prime Minister Mute Egede, who has stepped up a push for independence, has repeatedly said the island was not for sale and it was up to its people to decide their future.
