LOS ANGELES (Reuters) - The Los Angeles Dodgers beefed up their bullpen on Thursday by trading a pair of prospects for Baltimore Orioles closer George Sherrill.

The Dodgers (62-39), who hold a seven-game lead over the San Francisco Giants in the NL West, sent minor league third baseman Josh Bell and pitcher Steve Johnson to Baltimore, Major League Baseball website mlb.com said, citing baseball sources.

Sherrill, a 32-year-old left-hander, posted 20 saves with a 2.40 earned run average for the Orioles this year.

He is expected to serve as a set-up man for Los Angeles, tied with the New York Yankees for best record in the majors, but could share closing duties with Dodgers' reliever Jonathan Broxton.

(Writing by Larry Fine in New York, Editing by Sonia Oxley)