President-elect Donald Trump has named a Florida lawmaker to be his ambassador to Panama, days after he threatened to take back the Panama Canal.

Kevin Marino Cabrera, a Republican commissioner in Miami-Dade County, worked for Trump's 2020 campaign and this year was Florida's representative to the Republican National Committee.

Announcing his pick in a Christmas Day post on his Truth Social network, Trump said Cabrera "will do a fantastic job representing our Nation's interests in Panama!".

The president-elect repeated claims that Panama is "ripping us off" via shipping fees charged to use the Panama Canal, the main link between the Atlantic and Pacific oceans.

On Sunday, Trump told a crowd of conservative activists: "The fees being charged by Panama are ridiculous, highly unfair."

If shipping rates are not lowered, Trump said, "we will demand that the Panama Canal be returned to us, in full, quickly and without question".

Trump has also said he did not want the Panama Canal "falling into the wrong hands" and specifically cited China, which has significant interests in the waterway.

China is the second-largest user of the Panama Canal after the US, according to data. It has major economic investments in the country as well.

Responding to Trump's comments, Panamanian President José Raúl Mulino said "every square metre" of the canal and surrounding area belong to his country.

On Christmas Day, Trump fired off dozens of messages defending his policies and nominations, and repeated suggestions that the US annex Greenland and Canada.

It is unclear how serious Trump is about the territorial moves, or how they would be accomplished.

In one message he sarcastically wrote: "Merry Christmas to all, including to the wonderful soldiers of China, who are lovingly, but illegally, operating the Panama Canal" and claimed that "the United States puts in Billions of Dollars in 'repair' money, but will have absolutely nothing to say about 'anything'".

Up to 14,000 ships travel through the 51-mile (82km) canal each year, including container ships carrying cars, natural gas and other goods, and military vessels.

The canal was built in the early 1900s. The US maintained control over the canal zone until 1977, when treaties gradually ceded the land back to Panama. After a period of joint control, Panama took sole control in 1999.

Canal transit costs have increased over the past year due to a historic drought, according to shipping industry website Lloyd's List.

A Hong Kong-based company, CK Hutchison Holdings, manages two ports at the canal's entrances. But the Panamanian president has denied that China controls the shipping route.

"China does not control or administer the canal. When it comes to our canal, and our sovereignty, we will all unite under our Panamanian flag," Mulino said.