Donald Trump has offered Canada his full support in the government’s attempts to secure the release of two of its citizens facing the death penalty in China – despite telling Beijing he "appreciated" their tough sentences for drug crimes a week earlier.

The Canadian citizens, detained in apparent retaliation after the arrest of a Chinese executive at the request of the US, have been held separately for five months on charges of producing, smuggling and selling drugs.

Justin Trudeau, the Canadian prime minister, spoke with the US president by phone late on Thursday and urged Mr Trump to press for their release.

Two other Canadians are also being held.

A White House statement said the president expressed Washington's "solid commitment to standing by Canada in efforts to secure the fair treatment and release of Canadian citizens currently detained in China".

Inside Huawei's new campus for workers in China Show all 20 1 /20 Inside Huawei's new campus for workers in China Inside Huawei's new campus for workers in China An employee enters a train in the Huawei's Ox Horn campus at Songshan Lake in Dongguan Reuters Inside Huawei's new campus for workers in China A worker cleans a waterway as office buildings are seen at Huawei's new Ox Horn Research and Development campus in Dongguan, near shenzen Getty Inside Huawei's new campus for workers in China An area of Huawei's Ox Horn campus modelled after Cesky Krumlov in Czech Republic Getty Inside Huawei's new campus for workers in China The real Cesky Krumlov in Czech Republic Getty Inside Huawei's new campus for workers in China Employees sleep in their cubicle in the research and development area after lunch at the Bantian campus in Shenzhen Getty Inside Huawei's new campus for workers in China An area of Huawei's Ox Horn campus modelled after Heidelberg in Germany Getty Images Inside Huawei's new campus for workers in China Employees play basketball on a court within the staff housing complex at the end of the workday at the Bantian campus in Shenzhen Getty Inside Huawei's new campus for workers in China A replica of the Karl Theodor Bridge in Huawei's Ox Horn campus Getty Inside Huawei's new campus for workers in China The real Karl Theodor Bridge in Heidelberg, Germany Getty Inside Huawei's new campus for workers in China Huawei's Ox Horn campus at Songshan Lake in Dongguan Reuters Inside Huawei's new campus for workers in China Employees ride the bus home at the end of the workday from the company's Bantian campus in Shenzhen Getty Inside Huawei's new campus for workers in China Huawei workers eat their subsidised lunch in one of many large cafeterias at the company's Bantian campus in Shenzhen Getty Inside Huawei's new campus for workers in China Reception staff walk in front of a large screen showcasing different technologies in the foyer of a building used for high profile customer visits at the campus in Shenzen Getty Inside Huawei's new campus for workers in China An employee reads in the staff library on a break at the company's Bantian campus in Shenzhen Getty Inside Huawei's new campus for workers in China An area of Huawei's new Ox Horn campus modelled after a European City Getty Inside Huawei's new campus for workers in China Servers are seen inside Huawei's factory campus in Dongguan Reuters Inside Huawei's new campus for workers in China The conductor waits for a train in the Huawei's Ox Horn campus at Songshan Lake in Dongguan Reuters Inside Huawei's new campus for workers in China A general view shows the research and development centre at Huawei's Ox Horn campus AFP/Getty Inside Huawei's new campus for workers in China Employees works on a mobile phone production line at Huawei's factory campus in Dongguan Reuters Inside Huawei's new campus for workers in China An office building on the Huawei campus in Dongguan AFP/Getty

“They’re going to charge people with the highest level of crime," he told the audience at the Rx Drug Abuse and Heroin Summit. "And in China, unlike in our country, the highest level of crime is very, very high. It’s the ultimate. You pay the ultimate price. So I appreciate that very much.”

Donald Trump praises China for executing drug dealers: 'I appreciate that very much'

Mr Trump's intervention comes amid an ongoing trade war with the Chinese. American and Chinese negotiators are holding talks in Washington this week aimed at ending a dispute that has disrupted billions of dollars in trade.

Mr Trudeau made a plea for assistance from Canada’s southern neighbour as a former US national security adviser also weighed in on China’s detention of North Americans.

"Our free and open societies are under attack by an authoritarian closed mode," HR McMaster said.

“A model that not only is affecting the Chinese people by extinguishing their rights, their rights to free speech, their rights to privacy but it is also affecting other nations of the world.”

The diplomatic row between Ottawa and Beijing erupted late last year when a top Chinese executive was detained in Vancouver.

Meng Wanzhou leaving her home in Vancouver (Getty) (Getty Images)

On 1 December, Canadian police arrested Huawei’s chief financial officer Meng Wanzhou, who is out on bail while awaiting extradition hearings relating to fraud charges in the US. She is accused of using a subsidiary company to circumvent sanctions against Iran.

Following her arrest, China detained former diplomat Michael Kovrig and entrepreneur Michael Spavor in an apparent attempt to pressure Canada to release her. Neither have been given access to lawyers.

A month later, as the diplomatic row deepened, a Chinese court sentenced Canadian Robert Lloyd Schellenberg to death for drug smuggling.

Robert Lloyd Schellenberg attends his retrial in northeastern China's Liaoning province (AP)

He had originally been given a 15-year sentence after being found guilty in November, but prosecutors later said the sentence was too lenient.

A fourth Canadian – Fan Wei – was sentenced to death last week for drug trafficking in the southern Chinese province of Guangdong.

He was found guilty of producing and selling methamphetamine and another drug used for weight loss and treating ADHD.