US President Donald Trump has admitted to making up figures in a meeting with Canadian Prime Minister Justin Trudeau, according to reports.

The Washington Post reports President Trump boasted in a fundraiser speech on Wednesday that he made up information in the meeting with Mr Trudeau, where he said the US had a trade deficit with Canada despite having “no idea” if it was true.

Mr Trump reiterated his assertion that the US does have a trade deficit with its northern neighbour on Twitter on Thursday.

He also said it was other countries that refused to accept that such imbalances exist.

“We do have a trade deficit with Canada, as we do with almost all countries (some of them massive),” Mr Trump tweeted.

We do have a Trade Deficit with Canada, as we do with almost all countries (some of them massive). P.M. Justin Trudeau of Canada, a very good guy, doesn’t like saying that Canada has a Surplus vs. the U.S.(negotiating), but they do…they almost all do…and that’s how I know!

— Donald J. Trump (@realDonaldTrump) March 15, 2018

The Post obtained audio from Mr Trump’s 30-minute speech at a private fundraiser in Missouri, where he imitated and admitted to lying to the Canadian leader.

“Trudeau came to see me. He’s a good guy, Justin. He said, ‘No, no, we have no trade deficit with you, we have none. Donald, please,'” Mr Trump reportedly said.

“Nice guy, good-looking guy, comes in – ‘Donald, we have no trade deficit.’ He’s very proud because everybody else, you know, we’re getting killed.

“I said, ‘Wrong, Justin, you do.’ I didn’t even know. I had no idea. I just said, ‘You’re wrong.'”

The Post reported that after Mr Trump lied to Mr Trudeau, he asked a member of his staff to check if US did in fact have a deficit with Canada.

“I sent one of our guys out, his guy, my guy, they went out, I said, ‘Check, because I can’t believe it,'” Mr Trump said.

“‘Well, sir, you’re actually right. We have no deficit, but that doesn’t include energy and timber,” said the president. “And when you do, we lose $17 billion a year.’ It’s incredible.”

The figure is said to refer to the US-Canada trade balance if only goods traded are accounted for and services are removed from calculations.

Canadian foreign ministry spokesman Adam Austin said in a statement the US’ own figures show it has a trade surplus with Canada.

“Canada and the United States have a balanced and mutually beneficial trading relationship,” he said.

“According to their own statistics, the US runs a trade surplus with Canada.”

In 2016, the US exported $US12.5 billion ($16 billion) more in goods and services than it imported from Canada, leading to a trade surplus, not a deficit, The Post reported.

The US Department of Commerce reports the US ran a $US2.8 billion ($3.5 billion) trade surplus with Canada in 2017.