NEW YORK (CNN/Money) - McDonald's Corp. CEO Jack Greenberg said Thursday he plans to retire at the end of the year.

Greenberg, a 21-year veteran of McDonald's, will be succeeded by McDonald's Vice Chairman and President Jim Cantalupo, effective Jan. 1, 2003.

"In every company's history, there is a time when it is appropriate to pass the baton and give a new management team the opportunity to lead, and that time has come at McDonald's," Greenberg said.

The board of directors of the world's largest fast-food chain also named Charlie Bell, currently president of McDonald's Europe, as the new president and chief operating officer of McDonald's, and tapped Jim Skinner to be vice chairman.

Shares of McDonald's (MCD: Research, Estimates) fell in midday trading. They've fallen steadily in the second half of the year as the company has faced sagging sales and has struggled to find direction.

In early November, McDonald's warned about future profits and announced plans to cut costs, including closing 175 underperforming restaurants.

In October, the company said it planned to scale back its store openings in 2003 to focus more on growing sales at existing stores.

And in September, it warned that weaker-than-expected sales in the United States and Europe would hurt its earnings for the quarter and full-year 2002.

Against this backdrop, it seemed possible that Greenberg's decision to leave was one that may have at least been supported -- if not forced -- by the board of directors.

"[Greenberg] has been CEO for five years, and from what I hear everyone likes him," Morningstar analyst Carl Sibiliski told CNNfn. "The problem is, it has been a really bad five years, no matter how good he is."