Owners and representatives met for five hours yesterday with another similar session planned for today - and for most of next week.
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.
But despite fears the sport is heading into another period of industrial action, one leading baseball labour lawyer says a new contract can agreed without the need to strike.
Speaking to US media, Rob Manfred, baseball's executive vice president for labour relations, said: "I have said repeatedly, publicly, that I believe it is possible for us to reach a negotiated agreement without having an interruption of the season, and I still believe that."
