NJ Transit and the Brotherhood of Locomotive Engineers and Trainmen are set to meet today in Washington.
The meeting with the National Mediation Board is scheduled for 11 a.m.
The union is pushing for higher salaries, and tensions have escalated in recent days.
The two sides have traded personal attacks, and the gap between them appears wide.
If no deal is reached, a strike could begin Friday, disrupting commutes for hundreds of thousands.