There are cancellations and delays on Sydney's west and southwest train lines as the rail union industrial action continues.
The Rail, Tram and Bus Union is undertaking rolling stoppages and other action throughout August.
Workers refused to operate 37 trains on Monday, saying they did not meet minimum maintenance standards.
Sydney Trains CEO Matt Longland says the action is affecting trains on the T1, T2, and T8 lines and commuters should expect delays.
"That is creating gaps and will continue to create gaps across the day, mainly in the west and southwest," he told Sydney radio 2GB on Monday.
RTBU NSW secretary Alex Claassens said trains that did not meet minimum maintenance standards could be affected by a range of issues "from safety all the way through to cleanliness".
The rail union and management will meet again on Monday to try and resolve the long-running dispute over a new industrial agreement and the union's safety concerns with the mothballed Korean-built intercity trains.
Trains services will be stopped on Tuesday between 10am and 4pm on the Blue Mountains and Newcastle lines, affecting stops from Newcastle to Lithgow.
On Thursday, Sydney's City Circle line will be impacted with workers refusing to run trains from 10am to 4pm.
Premier Dominic Perrottet said trains being out of action was incredibly disappointing and dismissed the industrial action the union has been engaged in throughout this month as "political games".
He said Monday's action was "unplanned", although the union advised weeks ago it would not be operating trains that did not meet minimum standards.
The premier said the trains did meet those standards.
"This is just the union once again taking action and inconveniencing people for their own political benefit," he said.
The union was provided with a deed for changes to the new intercity fleet of trains on Thursday, although it was not the same one Mr Claassens signed in June.
The government wants signing the deed contingent on a new enterprise bargaining agreement being reached. The union wants them dealt with as separate issues.
The trains have been in storage since 2019 and the enterprise agreement expired in May 2021.
