Caterpillar Inc , the world's largest maker of construction and mining equipment, reported its first quarterly loss in 17 years on Tuesday, pulled into the red by more than half a billion dollars in charges from its wave of recession-triggered layoffs.

The company also slashed its full-year earnings and sales forecast, sending its shares lower in early trading.

Caterpillar, which has eliminated about 25,000 full-time and contract positions over the past few months, posted a first-quarter loss of $112 million, or 19 cents a share, compared with a year-earlier profit of $922 million, or $1.45 a share.

Sales fell 22 percent to $9.2 billion.

Caterpillar said it now expected full-year earnings of $1.25 a share, before restructuring costs, on sales of $31.5 billion to $38.5 billion. Three months ago, the company forecast profit of $2.50 a share, before restructuring, on sales of $36 billion to $44 billion.

Shares of Caterpillar were down 4.2 percent at $29.20 in trading before the market opened.

(Reporting by James Kelleher; Editing by Lisa Von Ahn)