Talks began a week ago, after Epstein and the Cubs agreed in principle to a five-year deal worth between $15 million-$20 million, sources said.
Recently the teams have been discussing minor leaguers as compensation, according to the sources.
Aside from compensation, another hold-up in the negotiations is believed to be which front-office personnel Epstein can bring to Chicago, according to ESPNBoston.com, which reported that the Red Sox were not going to allow Epstein to take any members of his inner circle. That could have changed, however, during negotiations.
Major League Baseball rules state a club has seven days to sign a person under contract to another team. This goes into effect after the team was granted permission to meet the employee. Teams can ask for an extension if the conversation appears to be ongoing, according to a major league source.
Epstein was still in Boston on Monday morning, according to a source.
Major League Baseball prohibits major announcements during the World Series, which starts Wednesday. However, there have been exceptions. In October 2009, the Cubs were able to announce the purchase of 95 percent of the team from Sam Zell and Tribune Co., by the Ricketts family for $855 million. The announcement came between the second and third games of the World Series between the New York Yankees and Phillies on a travel day.
Bruce Levine covers baseball for ESPNChicago.com and ESPN 1000.