Contract talks between Transdev and the Rail and Maritime Transport Union have been brought forward after industrial action has caused major disruption to the Wellington train network.
The talks which were scheduled for Thursday 26 September, have been brought forward to Monday 23 September.
"We encourage both parties to negotiate in good faith to resolve the situation as soon as possible," Metlink spokesperson Samantha Gain said.
"Due to ongoing industrial action, 21 Metlink train services were cancelled this morning between midnight and midday, 17 of which were replaced by buses.
"During that time, 147 scheduled services were able to run, meaning 12.5% of services were cancelled because of industrial action this morning."
More cancellations were expected this afternoon and this evening.
"A limited number of buses are on standby to replace cancelled services, including a wheelchair accessible shuttle," Gain said.
Passengers were advised to keep an eye on the service alerts and timetables on the Metlink website and app for information on delays.