NEW YORK (AP) — FedEx Co., the world's second biggest package delivery company, will lose more than 10 percent of its U.S.-based executives under a voluntary buyout plan.

The Memphis, Tenn., company says its personnel will leave the company in stages through May 2014.

On Wednesday a spokesman declined to say how many employees are leaving, or even how many U.S.-based officers and executives FedEx employs.

In December FedEx offered employees up to two years' pay to leave. It's seeking to reduce annual costs by $1.7 billion by 2016.

FedEx, the world's second biggest package delivery company, employs more than 278,000 people worldwide.

The news comes on the same day the U.S. Postal Service said it will end Saturday mail delivery to stem financial losses.