TORONTO (Reuters) - Hundreds of Canadian workers, many in the steel and aluminum sectors, have been laid off as a result of U.S. President Donald Trump's tariffs, according to a major union and companies.

Economists warned this was only the beginning as the impact of tariffs is expected to broaden the longer they are in place. Uncertainty surrounding Trump's policies has cast a chill over Canada's economy and labour market.

Trump imposed tariffs on steel and aluminum on March 12; more tariffs could be coming on April 2.

Marty Warren, national director of the United Steelworkers - the largest private-sector union in North America, with more than 225,000 members in Canada - said he has heard from members that about 200 of them are already out of a job.

Affected companies include Canada Metal Processing Group, which issued a February 24 press release announcing a workforce reduction of 140 employees due in part to "the threat of incoming tariffs from the United States on steel and steel derivatives." Those threatened tariffs are now in place.

The workforce reduction is a combination of permanent layoffs, temporary layoffs, work share and retirements, a company spokesperson told Reuters, adding the company is also freezing hiring for new or vacant positions.

Canada is the top supplier of steel to the U.S.

Warren told Reuters Ontario-based Algoma Steel ( ASTL ) has also laid off 27 people. Algoma Steel ( ASTL ) CEO Michael Garcia told Reuters the company had laid off about 20 people and could lay off more if they cannot find new Canadian customers.

"Everyone losing a job or laid off is a major hit," Warren said.

He said he expects "a tidal wave" next week, when a 30-day reprieve is expected to end for goods compliant with the trilateral U.S.-Mexico-Canada free-trade agreement.

"With the full-blown tariffs coming in on April 2 ... it'll probably affect 100,000 of our members."

Scott Noseworthy has worked as a shredder operator at the Canada Metal Processing Group's Ivaco plant in eastern Ontario for four years. Workers got notice of a potential layoff more than a month ago but were not certain it was happening until much later. They were hoping tariffs would be averted.

"When Trump imposed the tariffs it kind of hit us and brought us to a halt," he said. Now the plan is to be back at work this week but doing maintenance and clean-up work. After that, he does not know.

He said the uncertainty is tough with a two-year-old daughter at home.

"It's hectic: You're not sure whether or not you're going to have work one week to the next," he said.

Warren would like to see enhanced employment insurance and skills training for laid-off workers.

GOVERNMENT MEASURES

On Friday, days before calling a Federal election, Prime Minister Mark Carney announced measures allowing people earlier access to employment insurance.

This month Canada's federal government announced a multibillion-dollar aid program targeted at businesses, as well as a work sharing program providing employment insurance benefits to employees who work reduced hours.

Advocates and some economists say more is needed, including major overhauls to employment insurance that would allow more people to access it for longer, with a minimum weekly payment.

Making such changes as a pilot project is possible during a campaign, when Parliament is not sitting, said economist Armine Yalnizyan, Atkinson Fellow on the Future of Workers. Making it the norm would require legislation.

Carney's Labour Minister Steven MacKinnon was not available for an interview.

"The Government of Canada will continue to monitor impacts of tariffs across sectors and the economy and will bring forward additional measures to support workers and businesses as needed," department spokesperson Mila Roy wrote in an email before Friday's announcement.

Deena Ladd, executive director of the Workers' Action Centre, said her organization was already hearing from workers being laid off from smaller subcontractors and companies in the import-export industry, especially those with ties to the steel and aluminum industries.

"Things are changing every day. ... That uncertainty we've seen a lot of people talk about, that's no good for employers or for businesses. You can imagine how much more difficult it is for workers."