A month of industrial action that has caused widespread disruption to NSW train services will culminate with rail workers refusing to operate foreign-made trains.

The government and the rail union are blaming each other for the 24-hour strike on Wednesday, which will sideline foreign-made trains that comprise about 70 per cent of the fleet.

Sydney Trains chief executive Matt Longland advised commuters to avoid all unnecessary train travel on Wednesday, and work from home if possible.

Train services would be reduced to about a half-hour frequency on most lines, he said.

The T5 Cumberland line and and the T7 Olympic Park line will have no services.

“Avoid all unnecessary [train] travel and leave the capacity that is available on trains for those that really need it,” Mr Longland told Sydney radio 2GB on Tuesday.

“Work from home or avoid the trip on the train tomorrow.”

Rail, Tram and Bus Union NSW secretary Alex Claassens promised the month of targeted rolling stoppages and bans would be suspended on Wednesday and said September would be free of industrial action on the NSW rail network.

“We’ve actually guaranteed them peace until the end of September, or until the enterprise agreement gets voted up, whichever comes first,” Mr Claassens said on Tuesday.

Multiple unions are involved in the negotiations for a new enterprise agreement, to replace the one that expired in May 2021.

A separate fight continues over modifications to a fleet of mothballed Korean-built intercity trains the union believes is not yet safe to operate in the NSW rail network.

The government sent a letter to the union on Sunday dropping its request to make alterations to the trains dependent on a new enterprise agreement being finalised, and calling on the union to abandon Wednesday’s action.

The state government’s insistence the agreement be locked in before the modifications begin had been a sticking point in the protracted negotiations.

A deed for changes to the trains was negotiated further on Friday, but Mr Claassens said he had not been presented a copy to sign on Monday, dismissing the government letter as a stunt.

“It was a letter that was clearly designed for a purpose but it wasn’t designed for resolving our dispute,” he said on Tuesday.

Transport Minister David Elliott said he was disappointed by the union’s assessment of the letter.

“It was not a stunt. It’s exactly what the rail union asked for,” he said on Monday.

“Just take the deed … we’ve given you what you wanted.”

Mr Claassens said the union had made minor modifications during negotiations on Friday but did not receive confirmation the deed was suitable.

“Instead … we’ve been forced into another round of lengthy talks rather than getting on with the job of getting a signed deed which we can take to members and delegates to consider,” he said.

Negotiations continue.

– AAP