Boeing Co warned on Tuesday that it will conduct involuntary layoffs of engineers, part of an ongoing cost-cutting drive as the aerospace and defence company responds to increasing competition amid slowing aircraft sales.

The reductions, disclosed in an internal memo seen by Reuters, also include voluntary layoffs.

The memo did not indicate the number of reductions the company planned. It listed dozens of job categories eligible for voluntary layoffs in Washington state, southern California and South Carolina.

"While we have made good progress, more changes are needed to ensure our long-term future," John Hamilton, vice president of engineering at Boeing Commercial Airplanes, wrote in the memo.

"We continue to operate in an environment characterized by fewer sales opportunities and tough competition."