(Reuters) - Walt Disney Co <DIS.N> has agreed to buy 33 percent stake in the video unit of Major League Baseball's digital arm MLB Advanced Media in a deal valued at about $3.5 billion, Bloomberg reported, citing a person familiar with the matter.

Disney will also retain a four-year option to buy an additional one-third stake, Bloomberg said. (http://bloom.bg/29ute4B)

Disney and Major League Baseball could not be immediately reached for comment.

(Reporting by Supantha Mukherjee in Bengaluru; Editing by Savio D'Souza)