Thousands of NSW commuters have been left stranded with trains on the Sydney network and NSW TrainLink intercity rail passenger services cancelled because of an industrial dispute.

Sydney Trains CEO Matt Longland says commuters are in for "a very difficult" Monday with services suspended across Greater Sydney as well as the intercity network, affecting routes from Newcastle, the Blue Mountains and Kiama on the South Coast.

"We're urging customers to obviously avoid travel today or to use the transport journey planner to look for alternative options, such as buses, ferries and light rail if possible," he told Sydney radio 2GB.