PEORIA, Ill. (AP) – Heavy equipment maker Caterpillar Inc. posted a record first-quarter profit Monday and boosted its earnings forecast for the year amid a sales surge sparked by ongoing global demand for its hulking construction and mining machinery.

Caterpillar topped Wall Street’s expectations as earnings rose 45 percent to $840 million for the quarter that ended March 31, up from $581 million during the same period in 2005, when the Peoria-based company finished the year with record profit and revenue.

Profit per share was $1.20 for the January-March period, matching the company’s best-ever mark set in the last quarter of 2005 and up from 81 cents a share a year ago. Analysts surveyed by Thomson Financial had forecast profit of $1.05 per share.

Caterpillar, the world’s largest construction and mining-equipment maker, says low interest rates and inflation in check have fueled an upswing of construction and mining worldwide, boosting demand for its trademark yellow machines that include a mining truck as large as a two-story house.

“The demand is strong everywhere. … It’s hard to find a soft spot in their market,” said Alexander Blanton, an analyst with Ingalls & Snyder.

Despite record first-quarter earnings, Caterpillar shares dipped 9 cents to $77.78 in afternoon trading Monday on the New York Stock Exchange.

The company’s shares have traded in a 52-week range of $41.30 to $80, a record price posted last Friday.

Some analysts worry that Caterpillar’s first-quarter profit was bolstered by price increases over the past 18 months and say earnings could dip if costs for steel or other materials rise unexpectedly later this year.

“Any price spikes or shortages in these materials could put pressure on Cat’s margins,” Morningstar analyst Scott Burns said in a written statement.