The first of Sydney’s new intercity trains have been unveiled, but the government has no set date to operate the multi-billion dollar fleet as a union dispute drags on.

NSW Transport Minister Andrew Constance said on Tuesday the trains would begin arriving in sets of 10 each month from mid-2020. The fleet was originally due to be delivered from South Korea in early 2019.

State Transport Minister Andrew Constance aboard one of Sydney's new intercity trains. Credit:Nick Moir

Mr Constance blamed union disputes and the COVID-19 pandemic for delaying the trains, which will operate across the Central Coast, South Coast, Newcastle and the Blue Mountains.

"There was, last year, a lot of effort going into the design of the train which did put it back a couple of months," Mr Constance said as he unveiled the first of the 55 trains in Hurstville.