The NSW government is taking its battle with the rail union to the Fair Work Commission in a bid to stop it from disrupting Sydney's transport network for a second consecutive week.
The Rail, Tram, and Bus Union is locked in a long-running stoush with the government over the controversial Korean-made Intercity train fleet, arguing it has refused to sign a deal guaranteeing fixes to safety issues.
The government and the RTBU last week failed to broker an end to the dispute after the union knocked out 70 per cent of services on Friday, causing delays and cancellations on parts of the network.
More travel disruption is expected on the network this week, with the union foreshadowing similar action on Wednesday and Friday.
The government confirmed it had filed papers with the Fair Work Commission on Monday seeking orders to head off further action by the RTBU.
"We will be seeking to get a hearing in relation to those matters at the Fair Work Commission to stop industrial action," Premier Dominic Perrottet told reporters in Sydney.
An RTBU spokesperson told AAP on Monday the union had yet to receive confirmation of any government action against it at the commission.
The government has signalled a willingness to spend $264 million to modify the fleet, but the union insists it needs written confirmation as previous conciliatory offers were followed by backflips.
Transport Minister David Elliott has vowed to resign if he does not deliver on promises to the union and insists there are no safety concerns with the fleet.
Mr Perrottet on Monday reiterated the government's pledge to fix the fleet.
"We've said that publicly, we're making that a commitment," he said.
RTBU NSW secretary Alex Claassens said he was still waiting for a written document reflecting the government's promise to modify the fleet.
"It's outrageous that we're being forced to take action in order to get the NSW government to deliver on what should be a basic responsibility of government - providing a safe railway and fair working conditions for its workforce," he said in a statement on Monday.
Mr Claassens has said union action would continue to escalate "until such time as we have got a signed deed in our hand".
Labor leader Chris Minns urged "round the clock" talks and said the government needed to give the union written assurance on fleet safety upgrades.
"It shows rail workers and the travelling public that the government is serious about ensuring that those Korean-built trains are safe to use and work on the NSW public transport system," Mr Minns said on Monday.
Protected action on Monday would see trains sound their whistles, which would not impact on services in the state, the union said.
Other actions throughout the week are likely to include cleaners only working at their home depot and drivers not using the network to travel between stations.
