Atlanta-based Coca-Cola Co. has imposed a hiring freeze for most of its North American business unit, a part of Coke that has struggled to grow profits and volume.

The hiring freeze started July 1 and extends through Dec. 31, according to an internal memo obtained by Beverage Digest, a trade publication. The memo was sent by Coca-Cola North America President Sandy Douglas, Beverage Digest said in its Friday edition.

Glaceau, Fuze, Odwalla and Coke North America's Canadian unit are not part of the hiring freeze, Beverage Digest said. Glaceau is a division that makes Vitaminwater and Smartwater. Odwalla makes juices, and Fuze makes juice and tea drinks.

Coke's overall results have been on the rise. Global case volume increased 6 percent in the first quarter of 2008. Operating income was up 15 percent.

North America, though, has become a sore spot for Coke as the economy slows and U.S. consumers continue to shift away from carbonated soft drinks.

Coke's North American case volume was flat in the first quarter. Operating income in the first quarter fell 7 percent.

Coke confirmed the hiring freeze but would not elaborate on details. Coke plans to invest resources freed up from the hiring freeze to help build its business in North America, Coke spokesman Scott Williamson said.