U.S. President Donald Trump is vowing to press Chinese President Xi Jinping on Canada’s behalf over Beijing’s detention of two Canadians in apparent retaliation for Ottawa’s arrest of a Chinese telecom executive.

In an Oval Office meeting with Prime Minister Justin Trudeau Thursday, Mr. Trump said he would help Ottawa in the dispute, in which China is widely believed to be punishing Canada economically.

“Anything I can do to help Canada, I will be doing,” the President said when asked if he would help Mr. Trudeau get face time with Mr. Xi at next week’s G20 summit in Japan to push the Chinese leader on the detentions.

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U.S. President Donald Trump and Prime Minister Justin Trudeau met in Washington to discuss trade, USMCA and relations with China. After meeting with Trump and U.S. congressional leadership Trudeau took questions from the media. The Globe and Mail

Asked if he himself would raise the case with Mr. Xi, Mr. Trump said he would.

“I will, absolutely,” he said. “I’ll represent him well, I will tell you.”

Mr. Trudeau later told a press conference on the roof of the Canadian embassy in Washington that, “We absolutely expect that the subject of the Canadians arbitrarily and unjustly detained in China will be on the agenda.”

The visit was Mr. Trudeau’s third to Mr. Trump’s White House, in a relationship that has vacillated wildly with the whims of the mercurial President. At its nadir during last year’s G7 summit in Quebec, Mr. Trump attacked Mr. Trudeau as “weak” and “dishonest” on Twitter after the Prime Minister declared that he wouldn’t be “pushed around” by the U.S. President.

Mr. Trudeau jetted to Washington for the 90-minute sit-down with Mr. Trump – and a later meeting with House of Representatives Speaker Nancy Pelosi – to push the White House to increase pressure on Beijing and to encourage Congress to ratify the overhauled North American free-trade agreement.

Two sources with knowledge of the private discussions between the two leaders said Mr. Trudeau impressed upon Mr. Trump that Canada was being penalized by China for honouring its extradition treaty with the U.S. The Prime Minister argued that Canada and the U.S. had to have each others’ backs on China, and Mr. Trump agreed.

Mr. Trump was very interested in the cases of Michael Kovrig and Michael Spavor and promised to raise them with Mr. Xi, but did not make any specific commitments beyond that, the sources said. The sources were granted anonymity by The Globe and Mail because they were not authorized to speak publicly on the matter. One source said Mr. Trudeau did not ask Mr. Trump to withdraw the U.S. extradition request for Huawei Technologies CFO Meng Wanzhou, who is free on bail in Vancouver while her case is processed.

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Open this photo in gallery U.S. President Donald Trump meets with Canadian Prime Minister Justin Trudeau in the Oval Office of the White House June 20, 2019 in Washington. The two leaders were expected to discuss the trade agreement between the U.S., Canada and Mexico. Alex Wong/Getty Images

Mr. Trump, for his part, pushed the Prime Minister to ban Huawei from selling next generation 5G technology to Canada, one source said. The U.S. fears that Beijing’s spy agencies will use Huawei gear to eavesdrop on communications or shut down networks. Mr. Trudeau was non-committal in the meeting and told Mr. Trump that Canada was still conducting a cybersecurity review.

“We had an extended conversation on the situation Canada is currently facing in regard to China and the unacceptable situation that two Canadians are facing,” Mr. Trudeau said at the press conference. “We respect our partnership and our agreements including our extradition agreement with the U.S.”

In addition to seizing the two Canadians, China has also banned or restricted several Canadian imports, including canola and pork, inflicting financial pain on farmers.

Mr. Trudeau and Mr. Trump also committed to bilateral co-operation on supplying critical minerals to fuel both economies. Mr. Xi, who is embroiled in a trade war with Mr. Trump, has raised the spectre that China might ban exports of rare-earth minerals that are critical to major sectors of the U.S. economy.

“One thing the President and I discussed during our meeting was the need to improve our collective mineral security,” Mr. Trudeau said. “We agreed to … ensure future competitiveness of our mineral industries and the safety and security of our supply chains.”

The Thursday meeting was convivial, with Mr. Trump declaring that he and Mr. Trudeau would have “a positive day.” Mr. Trump did most of the talking during the brief, public portion of the meeting, sitting on the edge of his chair while Mr. Trudeau sat rigidly beside him, his hands clasped in his lap.

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The pair are on the same page on the U.S.-Mexico-Canada Agreement, the overhauled NAFTA: Mr. Trudeau wants the pact ratified to remove uncertainty for business and to take the issue off the table before the October federal election.

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The three countries reached the deal last fall, but it must be ratified by Congress to take effect. Congressional Democrats are demanding changes to the deal, primarily to strengthen enforcement of tougher labour standards in Mexico, before they will agree to vote for it.

Mr. Trudeau, however, said he did not want to renegotiate.

“We are concerned that any reopening of NAFTA could lead to not only lengthy further negotiations that we all were quite pleased were behind us, but also may lead to worse outcomes for Canadians,” he said.

It is possible, however, that Democratic concerns could be assuaged with a side deal between the U.S. and Mexico that would allow Canada to escape further involvement in talks.

Open this photo in gallery Mr. Trudeau is headed to the White House for what could prove to be a pivotal visit not only for North American trade and Canada's strained relationship with China, but for the campaign-bound prime minister himself. Sean Kilpatrick/The Canadian Press

One Canadian official said Mr. Trudeau focused in his meeting with Ms. Pelosi on selling the USMCA’s progressive elements on labour and the environment, which fit with Mr. Trudeau’s own centre-left agenda. The official said Democratic leaders insisted that they are sincerely interested in reaching a deal that would allow them to back USMCA.

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Ms. Pelosi presented Mr. Trudeau with a basket of California wine, chocolate and nuts after losing her bet with the Prime Minister on the outcome of the NBA Finals; Mr. Trudeau gave her several Toronto Raptors T-shirts and chocolate from Peace by Chocolate, a Nova Scotia company run by Syrian refugees.

Canada’s former ambassador to China, Guy Saint-Jacques, said it is a positive sign that Mr. Trump is prepared to raise the detention of the two Canadians with Mr. Xi, but only if he makes a strong case for their release. Mr. Saint-Jacques said little will be accomplished if the President simple mentions the issue as a favour to the Prime Minister – without making it clear that the U.S. expects the Canadians to be freed.

“I hope it is raised in very forceful terms, knowing that we are in this mess thanks to the U.S.,” Mr. Saint-Jacques said. “Trump could tell Xi, ‘Look, don’t go after the Canadians, you are angry at me. They have arrested Ms. Meng because I asked for that so stop punishing the Canadians and free the two guys you arrested.’ But would that be accompanied by some kind of a threat so that Xi would know that Trump is very serious?’’