The solar energy industry made an eleventh-hour plea to President Trump on Wednesday not to impose restrictive new tariffs on solar panel imports, warning of a massive round of layoffs.

"I am writing you on the eve of your decision on solar tariffs to make a personal plea to consider the real impact on American jobs and our economy," wrote Abigail Ross Hopper, CEO of the Solar Energy Industries Association, in a letter to Trump.

The president must decide by Friday whether to impose tariffs on solar panel imports, which was recommended by the International Trade Commission.

"A decision to impose high tariffs in line with the International Trade Commission’s recommendation will lead to the layoff of tens of thousands of workers, cause companies to stop investing in the United States and bring an American economic engine screeching to a halt," Hopper said.

The trade commission voted in favor of the protectionist action in response to petitions by two bankrupt companies, Suniva and SolarWorld, that make solar panels in the U.S. but are owned primarily by foreign investors.

"Ironically, the very jobs we all want to grow, American manufacturing jobs, will retract as the number of projects are scaled back significantly," Hopper wrote.

The tariffs would drive up the cost solar panels, forcing solar installation firms, steel workers and other industries that contribute to solar to cut jobs.

"This is not hype, this is what will happen," she said.

"American companies manufacture, among other things, steel and aluminum racking systems, inverters, and tracking devices," Hopper said. "Raising solar prices, as these tariffs would do, would reduce demand for those downstream products and kill manufacturing jobs."

Hopper included quotes from workers in the solar sector to illustrate her point.

“When we first heard about the trade case at the site, everyone immediately started signing letters to their congressmen and women to let them know how important these jobs are not only to the solar industry, but local communities,” Li-Anh Bayard, project administrator at Raleigh, N.C.-based Swinerton Renewable Energy, said in the letter.

DeJuan Humphries, a crew lead at New Columbia Solar in the District of Columbia, said the idea of new tariffs was “very upsetting," because of the impact it would have on his well-being and family.

"You know I count on this job pretty much to provide for my family," Humphries said. "I’m a single dad. So pretty much it would definitely be an unfortunate situation if something like that happened.”