US President Donald Trump has threatened to impose 50% tariffs on Canadian planes in retaliation for Canada "wrongfully, illegally, and steadfastly" refusing to certify a number of planes made by US firm Gulfstream.

In a social media post, Trump also said he was "decertifying... all Aircraft made in Canada", although the White House later reportedly walked back that claim.

Also on Thursday, the president pledged new tariffs on countries that sell oil to Cuba, as the US steps up its pressure on the Caribbean nation's communist leadership.

The proposed new levies were outlined in an executive order, although no details were given about specific tariff rates or which countries could be targeted.

Trump said the US would decertify all Canadian aircraft, including planes from its largest aircraft maker, Bombardier.

"We have taken note of the post from the President of the United States to social media and are in contact with the Canadian government," Bombardier said in a statement.

But a White House official later told the Reuters news agency that Trump was not suggesting decertifying Canadian-built planes currently in operation.

The BBC has contacted the White House, the US Federal Aviation Authority and the Canadian government for comment.

Trump's latest threats against Canada come at a time of heightened tensions between the neighbouring countries.

Earlier in January, Canadian Prime Minister Mark Carney made global headlines for his speech at a World Economic Forum event in Davos in which he indirectly called out Trump for a "rupture" in the postwar world order.

Later in the month, Carney visited China where he announced a "strategic partnership" with Bejing, and agreed to reduce some tariffs.

This prompted Trump to threaten a 100% tariff on Canadian goods if the country struck a trade deal with China.

Trump has also continued his campaign against Cuba, threatening tariffs on countries that supply oil to the Caribbean island nation.

On Tuesday, Trump said Cuba "will be falling pretty soon", as long-time ally Venezuela no longer sends oil or money to the country after President Nicolás Maduro was seized by US forces on 3 January. Previously, the South American nation was believed to be sending about 35,000 barrels of oil a day to Cuba.

In an executive order on Thursday, Trump said "the policies, practices, and actions of the Government of Cuba constitute an unusual and extraordinary threat".

He also accused Havana of hosting "dangerous adversaries of the United States".

The tariffs may target countries "that directly or indirectly sells or otherwise provides any oil to Cuba".

Trump has previously ordered Cuba to "make a deal, before it is too late", although he has not specified the terms of a deal or the consequences that the island nation could face.

At the time, Cuba's President Miguel Díaz-Canel said Washington had no moral authority to force a deal on his country.

The Trump administration's tactic of confiscating sanctioned Venezuelan oil tankers has already begun to worsen a fuel and electricity crisis in Cuba.

The country has faced rolling blackouts, with Cubans struggling to cope without reliable electricity supplies.

Cuban foreign minister Bruno Rodriguez recently said that the Caribbean island nation had "the absolute right to import fuel" from any willing exporter "without interference or subordination to the unilateral coercive measures of the United States".

The BBC has contacted the Cuban Foreign Ministry for comment.