HARTFORD, Conn. (AP) — Sikorsky Aircraft Corp. announced on Thursday that it is trimming its worldwide workforce of 18,000 by about 540 jobs to remain competitive in the helicopter design, manufacturing and service industry.

Paul Jackson, the company's director of communications, called the move to cut about 3 percent of the workforce "a difficult decision." The company is not disclosing a breakdown of where the job cuts will be.

Sikorsky is headquartered in Stratford and has about 9,000 employees in Connecticut.

Jackson said the company does not yet know how many layoffs will be necessary until it is clear how many of the eligible unionized workers in Connecticut accept a voluntary separation package.

He said Sikorsky, whose parent company is the Hartford-based United Technologies Corp., has experienced strong growth while other manufacturers have had to downsize, move or close. Still, he said, the company needs to reduce its workforce as it goes forward.

"Our sales have increased nearly 40 percent since 2007, and we've been able to expand our workforce by nearly 59 percent since then. But those rates aren't sustainable," Jackson said. "We are entering a new world, with moderating growth in line with U.S. and international economies and their impact on our commercial and military customers."

All five branches of the U.S. armed forces use Sikorsky helicopters, as well as military and commercial operators in 40 nations, the company's website says.

In the U.S., Sikorsky has manufacturing and assembly plants in Stratford, Troy, Ala., and West Palm Beach, Fla. The company also has engineering and design centers in Alabama, Kentucky, Montana and Texas. In addition, Sikorsky has manufacturing and assembly facilities in Mielec, Poland, as well as joint venture manufacturing operations in Turkey and China. Sikorsky has a presence in other states and countries as well.