The Berejiklian government and rail union are heading for a showdown with the arrival of the first of $1.6 billion worth of new intercity trains from South Korea next month, due to claims that they have been "specifically designed to get rid of guards".

The first two of 55 intercity trains on order will arrive at Wollongong's Port Kembla on or about December 17, about eight months later than originally planned.

Transport Minister Andrew Constance and an artist's impression of an intercity train. Credit:Janie Barrett

Commuters will have to wait until at least March to ride on the first of the new double-deck trains from Sydney to the Central Coast and Newcastle because they are required to undergo rigorous testing on local tracks before they are permitted to carry passengers.

Their arrival just days before Christmas is set to ignite a battle between the government and unions about whether the state intends to keep guards on the new trains in the longer term.