Americans are hitting the brakes on new motorcycles from the country's best-known maker.

Harley-Davidson warned Tuesday that its full-year bike sales and profit margins would fall well short of its expectations, concerning investors who were already fretting about the industry's struggles to draw in Millennials.

The manufacturer also plans to cut jobs to compensate for the disappointing sales, though the number of positions wasn't immediately clear.

The company's stock, trading under the ticket symbol HOG to reflect the nickname for Harley bikes, slumped 7% to $46.36 as of 2:30 p.m. Eastern.

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Harley said its full-year shipment of motorcycles to dealers would fall by 6% to 8% from last year, marking a sharp decline from its previous projection of "flat to down modestly."

The new projection includes a 10% to 20% decline in the third quarter, as well as a full percentage point drop in operating profit margin for the full year.

"While we expected the U.S. industry to be challenged, we were disappointed by the unexpected magnitude of the industry softening in the quarter," Harley CEO Matt Levatich told analysts.

He said the company would slash hourly jobs at "some of our U.S. manufacturing plants" beginning immediately. A spokesperson declined to comment on how many jobs would be lost.

Despite the challenges, Levatich said the company's innovative 2018 model-year motorcycles would provide a lift.

But investors are concerned that Millennials aren't interested in the "hog" lifestyle that energized previous generations.

Levatich said Millennials were buying used bikes in encouraging numbers, but the company must persuade them to buy new motorcycle.

"It's up to us to inspire even more of them to ride and to engage with Harley-Davidson's products and experiences," he said.

The dour outlook comes amid speculation that Harley is weighing plans to pursue a $1.7 billion acquisition of rival motorcycle maker Ducati. With sales slumping, the company could face increased urgency to get a deal done because Ducati sales are up 13% over the past two years, according to UBS.

For Harley, second-quarter revenue fell 4.8% to $1.77 billion, and net income declined 7.7% to $258.9 million, compared with the same period last year.

Global sales of motorcycles declined 6.7% to 81,388. That included a 9.3% decline in the critical U.S. market, where the company sold 49,668 units.

Contributing: Milwaukee Journal Sentinel reporter Rick Barrett

Follow USA TODAY reporter Nathan Bomey on Twitter @NathanBomey.