Team owners and player representatives met on Thursday and Friday of last week and will continue today.
They are locked in discussions over revenue-sharing proposals which could see wealthier clubs such as the New York Yankees transferring some of their revenues to less wealthy teams. The union has proposed that $228million (EUR227m) should be transferred from richer to poorer clubs.
Along with revenue-sharing, the two sides also talked about compensation for players and possible changes in player contracts if they are injured.
Still yet to be discussed is what will replace MLB's labour agreement, which expired last November. Since then players have been working under the terms of the old contract.
The union is threatening to strike because it is worried that owners might declare a deadlock in talks and not introduce new work rules until after the season.
After a four-hour session on Thursday, after which there was a feeling of optimism that a deal could be reached, Friday's session lasted just one hour.
Parties have confirmed they will be available all week for talks.
