The Rail, Tram and Bus Union met with Transport Minister David Elliott on Tuesday to try and hammer out a resolution to the workplace fight that has caused limited train services to run on Tuesday after a system-wide shutdown on Monday.
The meeting between union officials and the minister lasted about an hour and concluded around 10am but nothing of substance was agreed, AAP understands.
The meeting reportedly included full and frank exchanges between the parties.
RTBU NSW Secretary Alex Claassens said there was an initial "blood-letting" at the meeting, followed by a discussion about the way forward out of the crisis.
"We want an outcome, we need an agreement," Mr Claasens told Sydney radio 2GB.
Sydney Trains and NSW Trainlink remain before the Fair Work Commission, along with the union, to resolve issues surrounding negotiations for a new enterprise agreement.
The FWC hearing is expected to conclude on Wednesday.
As the dispute drags on, trains are running at 25 per cent capacity on Tuesday, with most trains timed every 30 minutes, while services on Sydney's inner-city rail network are reduced to every 15 minutes, and buses are supplementing some services.
Sydney Trains says commuters can expect a limited service for days, before frequency increases later in the week, and train passengers are being urged to find alternative transport.
Meanwhile, the union says its members were trying to get as many trains on the tracks as possible on Tuesday, and warns it's likely the same level of service will run on Wednesday.
"We worked until late last night to try to get a resolution and today we are running trains and we will make sure they run safely," Mr Claassens told ABC TV.
The government and union have blamed each other for the sudden cancellation of Monday's rail services, which inconvenienced around half a million commuters.
Government transport authorities said they were forced to shut down the network because of unspecified safety concerns, but the rail union maintained its planned, limited industrial action would not have affected safety and workers were ready to run the trains.
The move by Transport for NSW blindsided commuters, with many left stranded across Sydney, Newcastle, the Central Coast, Blue Mountains and Illawarra during the morning peak and the rest of the day.
Premier Dominic Perrottet on Monday blamed the union for the shutdown, saying it was part of a "coordinated, concerted attack" on the government by the union and Labor.
He was angry the trains were out of action on the same day Australia's borders reopened to international tourists, as children were trying to get to school and university students were returning to campus.