Workers complete a truck's engine on the assembly line at the Toyota Motor Corp. manufacturing facility in San Antonio, Texas

Toyota Motor and Mazda Motor are set to unveil plans for a $1.6 billion assembly plant in Huntsville, Alabama, sources familiar with the matter tell CNBC.

That announcement is expected to be made Wednesday afternoon in Alabama. Toyota executives and Alabama Governor Kay Ivey are slated to attend that announcement, sources said.

The plant, which will build the Toyota Corolla along with other models, is a huge win for President Donald Trump's administration which has made a point of stressing it would add manufacturing jobs, especially in the auto industry.

The plant is projected to employ about 4,000 workers and produce approximately 300,000 vehicles a year.

A spokesperson for Toyota declined to comment to CNBC.