As the president of a steel company, David Zalesne said some of the Trump administration’s economic policies are probably going to be good for his industry. President Trump has vowed to bolster American manufacturing — and domestic steel production in particular.

But a push to end a program that shields the children of undocumented immigrants from deportation, a move the administration has been considering, seems “self-defeating,” Mr. Zalesne said.

On Tuesday, Mr. Trump is expected to announce his plan for the program, known as Deferred Action for Childhood Arrivals, or DACA. While he may decide to give Congress time to come up with a permanent resolution, immigration advocates and economists warned that the possible demise of DACA could lead to the deportation of as many as 800,000 people, many of whom are working legally in industries across the United States.

“Why would you take people out of the work force, who are part of the system and paying taxes?” asked Mr. Zalesne, president of Owen Steel in Columbia, S.C.