Some laid-off employees of Caterpillar have received good news that thanks to improvement in the global economy, the construction equipment manufacturer has begun bringing back approximately 550 U.S. employees. Some have already returned to work while the remainder will during the course of 2010.

But the company also said it will officially notify 2,500 other employees who were previously laid off that they will not be returning to work. Cat said a separation package will be offered, and that the cuts are necessary as the company “aligns production levels with demand and resource requirements.”

“We are pleased that signs of recovery in the global economy allow us to return a selected group of laid off employees to work,” Caterpillar chairman & CEO Jim Owens said in a press release. “But it’s important to remember that we are not close to the record-breaking demand we experienced from 2004 through 2008.”

Last week, Cat outlined its forecast for 2010, predicting sales of 10 to 25% higher than 2009, which it is saying will be $32 to $33 billion.