NEW YORK -- Starbucks says its chief operating officer, Troy Alstead, is taking an "extended unpaid leave" after 23 years with the company.

The Seattle-based coffee chain said it would provide more details on its transition plan during its quarterly earnings call slated for Jan. 22. Alstead's last day will be March 1, the company said.

Starbucks spokesman Jim Olson did not say whether Alstead would be returning. He said it was a "very personal decision," and that Alstead had been discussing it with CEO Howard Schultz for some time.

Olson added that Alstead had planned on a similar move in 2008, but that Schultz persuaded him to stay with the company at the time.

In after-hours trading, Starbucks shares slipped 2.4 per cent, or $2, to $80.49.

Alstead's upcoming departure comes as Starbucks seeks to expand beyond its popular lattes and Frappuccinos. To continue driving sales growth, the company has introduced new and revamped food offerings -- such as warmed up sandwiches and salad boxes -- intended to attract customers in the slower afternoon hours.

In the evenings, the company has said it plans to make beer and wine available in up to 25 per cent of its 12,000 U.S. stores over the next five years. That "evenings" program, which includes small plates such as chicken skewers after 4 p.m., is already in select stores around the country.

Alstead, 51, has been with Starbucks Corp. in a variety of leadership roles, including chief financial officer.