Volkswagen’s truck unit warns that the chip crisis will undercut sales.

Volkswagen’s truck unit is facing “severe difficulties” in buying semiconductors that are weighing on sales at a time when demand is rising, the company warned on Wednesday, offering the latest sign of how a global chip shortage is holding back economic growth.

Traton, the maker of Scania, MAN and Navistar trucks, said it was also suffering from shortages of other critical components.

The shortages come as the global economy is slowly rebounding as new coronavirus cases decline and consumers spend money saved during pandemic lockdowns. To meet demand, the company is cannibalizing parts from finished but unsold vehicles and installing them in trucks for which there are firm orders.

As a result, sales from July through September will be “significantly lower than planned” even though customers are clamoring for trucks, Traton said. “Supply chain difficulties will have a stronger impact than expected.” Volkswagen owns 90 percent of the truck maker, which has a separate listing on the stock market.

Raw materials like steel and aluminum have also become scarcer, in part because manufacturers did not expect demand to bounce back so quickly. The shortages are preventing the global economy from recovering from the pandemic as fast as it could otherwise.

“It is not just the semiconductor issues stretching global supply chains at the moment — it is also the shortage of numerous other products,” Matthias Gründler, the chief executive of Traton, said in a statement. He said he expected the shortages to continue into 2022.

Trucks increasingly come with autonomous driving features and other sophisticated electronics that require semiconductors. Chip makers were not prepared for the increased demand from vehicle manufacturers, and have struggled to maintain production in the face of lockdowns in places like Malaysia, an important semiconductor producer.

A top executive at Daimler’s truck unit said earlier this week that it, too, was suffering. “The situation has become more challenging for us” in the third quarter, Karin Radstrom, the head of Mercedes-Benz brand trucks, said during an online news conference on Tuesday.

“We are currently really fighting for every truck to get it out of the gate,” Ms. Radstrom said, “because the customer demand is very, very good.”