As Prime Minister Mark Carney prepared to enter the belly of the beast with his Oval Office meeting with U.S. President Donald Trump on Tuesday, those representing Canadian industries threatened by Trump's tariffs were bracing themselves.

The Canadian auto industry, one of those suffering the most from steep U.S. tariffs, tempered expectations of the high-profile meeting between the two world leaders on Tuesday.

But Canadian steelworkers warned that it would be a grave political miscalculation for Carney to return empty-handed — a sentiment Conservative Leader Pierre Poilievre pounced on in Monday's question period.

Representatives of the auto industry told The Canadian Press they'll be looking for positive signals — but not much more.

Brian Kingston, president of the Canadian Vehicle Manufacturers' Association, said this meeting is likely just one part of ongoing discussions and he's not holding his breath for an immediate outcome.

"I don't expect that we're going to see an agreement that removes all tariffs on automotive," he said.

Kingston said the tariffs are doing great damage to his industry and manufacturers' costs are mounting with each day that goes by without an agreement.

"This is unsustainable and it is ultimately doing severe damage to the North American auto sector. So we need agreement and we need it now," he said.

Flavio Volpe, president of the Automotive Parts Manufacturers'​ Association, said he hopes to see some positive signals coming out of the working meetings.

"It's good, especially with this president, to have (those) face to face," Volpe said. "I'm happy that Team Canada is going down there. We were there last week. I didn't really hear a lot of urgency from American voices on Canadian interests, so hopefully this refreshes a lot of their minds on just how close we're integrated."

Global Automakers of Canada Vice President Lucas Malinowski said "we're all going to be waiting with bated breath and hoping for the best." He said he will be watching for anything that affirms Trump is committed to renewing the Canada-United States-Mexico Agreement on trade.

"Having some clarity on the ongoing durability of that agreement, I think, will be critical to give certainty to the auto industry," he said.

A spokesperson for the Canadian Steel Producers Association declined an interview request by The Canadian Press, saying only they'll be watching the meeting closely.

But Marty Warren, national director of the United Steelworkers union, said he worries the meeting could produce a "half-measure" on steel that the prime minister might "try to sell as a victory."

"He's raised a lot of expectations and there's a lot of people, not only in steel but softwood lumber as well and aluminum, that feel if he's going down, he should becoming home with something," Warren said.

"I'm sure Poilievre will let him know that if he comes home empty handed."

Poilievre offered Carney support in a letter ahead of the meetings, writing that his party is offering to "help you keep your promise to ‘negotiate a win’ on tariffs with the U.S."

The Conservative leader also sought to keep up the pressure on the Liberals in the House of Commons on delivering tangible results.

"Surely, after promising to negotiate a win, to have a deal by July 21, the prime minister is not flying all the way to Washington, D.C. just to have lunch? By the sounds of it, that is all the Liberals are going to accomplish," Poilievre charged in question period debate Monday.

Intergovernmental Affairs Minister Dominic LeBlanc replied that Ottawa has said consistently it has "work to do with our American partners on sectoral tariffs."

"Was the leader of the opposition suggesting that if the president of the United States invites us to go to Washington for a meeting and a working lunch, we should have just said, 'No', and hung the phone up?" he said.

Partisan pundits on evening TV politics shows warned that Carney will look weak if he emerges with little to show.

But Alberta Premier Danielle Smith, who met with Carney on Monday, wished him well and said she'd "love to see a renegotiated Canada-U.S. free trade agreement sooner rather than later.”

Trump announced new tariffs on social media Monday, warning he plans to impose a 25 per cent tariff on medium and heavy-duty truck imports on Nov. 1, a move widely seen to be aimed at Mexico.

Fraser Johnson, a professor at the Ivey Business School, said Canada's medium and large, heavy-duty truck market is fairly small.

"It's not going to move the needle much. It's not like automobiles and light trucks. It's not like lumber. It's not like steel," he said.

Mexico is the largest exporter of such trucks to the U.S., although the latest move will still affect Canadian companies in a variety of ways.

"Aluminum and steel have been probably the (tariffs) impacting us the most, but this latest one will impact a few of the original equipment manufacturers that have plants in Mexico," said Jean-Marc Picard, general manager of the Canadian Transportation Equipment Association that represents commercial truck manufacturers.

– Kyle Duggan, The Canadian Press