Caterpillar Inc. on Tuesday reported lower quarterly net profit that missed expectations as lower prices for copper, coal and iron ore hurt mining equipment orders, and warned the recent fall in oil prices would make for a difficult year in 2015.

The report sent the company's shares down nearly 6 percent in premarket trading.

The world's largest maker of construction and mining equipment said it expects only a modest improvement in the global economy in 2015 and gave an earnings outlook for the year below Wall Street estimates. Chief Executive Officer Doug Oberhelman said without a doubt Caterpillar faces a "tough year in 2015."

"While 2015 will be difficult, the work we've done to improve our cost structure, market position and quality will position us for better results when the world economy and the key industries we serve improve," Oberhelman added.

The Peoria, Illinois-based company reported fourth-quarter net profit of $757 million, down nearly 25 percent from $1.03 billion a year earlier.

Caterpillar reported earnings per share of $1.23, compared with $1.54 a year earlier. Analysts expected $1.55 for the most recent quarter.

Revenue totaled $14.24 billion, down from $14.4 billion a year earlier, but above expectations of $14.18 billion.

Caterpillar said it expects full-year 2015 earnings per share of $4.60, or $4.75 excluding restructuring costs. Analysts estimated $6.67 for the year.

In premarket trading Caterpillar shares were down nearly 8 percent at $79.25.