Premier Chris Minns says he is not confident crisis talks today will provide a breakthrough, ahead of planned industrial action on Sydney's rail network.

The NSW government is expected to meet with the union representing rail workers later today as a deadline to halt train services over coming days looms.

"We're going to try and do everything we can to solve this dispute on behalf of the people of New South Wales, it's important that we acknowledge that we're not confident of an imminent breakthrough," Mr Minns said.

The Rail, Tram and Bus Union (RTBU) has instructed its members to not operate the Sydney Train network from first thing Friday to Sunday morning as part of an industrial action, but union secretary Toby Warnes blamed the government for the shutdown for not capitulating to its demand to run around-the-clock weekend services.

"We ran services perfectly last weekend, they can run services perfectly again this weekend," he said.

"Our action was designed to ensure that commuters could still get around during festive season. In fact, they could get around better.

"We hope that the premier intervenes [in negotiations] and we see some sense."

Transport for NSW is preparing for alternative services, including buses for major events over the weekend and school services.

Transport Minister Jo Haylen said ongoing talks with the union yesterday led to an agreement that services would continue on Thursday, ensuring people attending the Pearl Jam concert in Sydney Olympic Park that evening could catch a train home.

"But we've got to be very clear here that the actions are still in place for Friday and Saturday, causing potential massive disruption to our network and meaning that people can't get where they need to go."

The industrial action represents an escalation in negotiations between the RTBU and the government on a new enterprise agreement.

The union demanded the government operate 24-hour train services throughout the weekend, like it did a week earlier.

But the government shot it down, offering to run only the Strathfield to Hornsby line around the clock.

Passengers warned to 'prepare now'

Sydney Trains chief executive Matt Longland said a normal timetable cannot operate unless union members worked on the weekend.

"The RTBU are saying that members will not operate services on Friday or Saturday and into Sunday morning. That is not just train drivers. That's people that work at stations… people that keep the network running," he said.

Operators around the public transport network are "scrambling" to fill transport gaps for commuters, who are being warned to expect delays.

"Prepare now," Transport for NSW secretary Josh Murray said.

One of the key events of concern is a second Pearl Jam concert taking place on Saturday night at Sydney Olympic Park. 

Mr Murray said 30,000 people were expected to attend with a significant amount travelling from the Central Coast and Newcastle. 

"Plan early because we cannot yet rely on having a clear path to Sydney Olympic Park or home again if you are coming from out of Sydney," he said.

Commuters are being warned Sydney's roads are also expected to be severely impacted by the shutdown as more people are forced to drive.

Workers are being encouraged to make alternative arrangements if possible especially on Friday. 

Network struggles to maintain services

The showdown comes as the train network struggled to maintain some services yesterday afternoon, with Sydney Trains warning more instability is expected in the lead up to the industrial action.

"We had more than 100 train services delayed or cancelled [yesterday] across Sydney," Mr Longland said.

"It is a very challenging period, as more and more of these industrial bans are put in place, it becomes more difficult to keep the network operating."

This morning the network faced cancellations on its inner-city line impacting services travelling from Gosford and Newcastle.

Meanwhile, Mr Longland said industrial action today will lead to buses replacing trains on the Blue Mountains line for three hours during peak commutes.

Mr Warnes denied industrial action is behind the delayed and cancelled services that have hampered the network since yesterday, claiming the government is misinforming the public.

"Our teams are doing their very best, and we ask passengers to please be respectful of our staff," Mr Longland said.

The proposed weekend shutdown of rail services across the Sydney train network has already started impacting services on the south coast.

NSW Trains said some afternoon services may be delayed or cancelled today due to protected industrial action.