WHITEHOUSE STATION, N.J. — Merck & Co. is planning to phase out operations at eight research sites and eight manufacturing sites.

It is also continuing to consolidate office facilities worldwide as part of the global merger restructuring program that began last December following its acquisition of Schering-Plough Corp.

The company explained that the goal of the restructuring is to create a flexible research and development organization that cultivates scientific innovation, facilitates external collaboration and drives pipeline progress.

In addition, Merck expected its total work force to be reduced by about 15% across all areas of the combined company worldwide as part of the initial phases of its merger restructuring program. It stressed that it would continue to hire new employees in strategic growth areas of the business as necessary.

"Today’s announcement is another important step as we successfully integrate our global operations on schedule and move forward with Merck’s strategic priorities," said Richard Clark, chairman and chief executive officer. "These changes are crucial to drive growth and realize the promise of being a global health care leader for the long term.

"While we believe these actions are necessary to support Merck’s competitive advantage, they required difficult decisions that will impact some of our colleagues, their families and local communities. We will implement our restructuring plans with the utmost care and respect for the hard-working and talented employees of Merck."

Merck said it remained committed to achieving its previously announced synergy target of $3.5 billion in ongoing annual savings in 2012.