The sides resumed discussions at the league's Manhattan offices with just over three days remaining before their collective bargaining agreement expires.
It's the first formal session they've held since Aug. 31.
NHLPA executive director Don Fehr wouldn't confirm a proposal from the union is coming, but said: "We have some things to tell them today."
Prior to the meeting, deputy commissioner Bill Daly told The Canadian Press that he expected the union to deliver an "agenda" or "message," if not a proposal.
With Saturday's deadline of 11:59 p.m. ET looming for a lockout, it promises to be an important few days.
The union will open a meeting with some 300 players later in the day while the NHL's board of governors is scheduled to convene on Thursday.
Meanwhile, the union says it has filed an application with Quebec's labour relations board, along with at least 16 players of the Montreal Canadiens, asking it to declare a lockout illegal in the province.
A hearing on the application is scheduled for Friday morning in Montreal.