"It's all driven by Ford demand, or lack thereof," said Roy Wiley, spokesman for the Warrenville, Ill.-based engine maker. "High diesel fuel prices, the housing market - you name it."
Officials of United Auto Workers Local 98 could not be reached for comment.
Laid-off workers will return the week of June 23, prior to a regularly scheduled three-week summer shutdown to begin June 30.
An unspecified number of workers in a machining shop and the company's nearby casting plant would not be affected.
International supplies diesel engines to Ford Motor Co.'s Louisville truck assembly plant, which is closing for a month due to slowing demand.