The new South West Metro set to open this month in Sydney has run into a slight issue.

The trains do not fit perfectly into some of the platforms on the new line to Western Sydney.

WATCH THE VIDEO ABOVE: New South West Metro encounters safety issues with some train doors.

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The problem will only affect certain doors on the Metro trains, those that line up with curved parts of platforms where the distance between train and platform are the widest.

Six doors in total are affected on the M1 line from Sydenham to Bankstown, and those doors will remain locked at the affected stations due to safety concerns.

Commuters heading to Dulwich Hill, Canterbury, Campsie or Marrickville will need to move to an unaffected exit when getting off at these stations.

Transport Minister John Graham defended the rollout of the $30 billion project which has been years in the making.

“I don’t accept that it’s gone wrong,” Graham said.

“This train will be running. These communities will have a Metro service every four minutes very, very soon,” he said.

The new South West Metro line set to open this month has run into a slight safety issue with some of the train doors. Credit: 7NEWS

Graham did not say how long it will take for the safety issues to be fixed.

An official opening date for the South West Metro is also yet to be confirmed.

The new service will put Bankstown just 28 minutes from the Sydney CBD.

Transport officials are already forecasting higher passenger demand than originally expected, with an extra 2500 passengers between 8am and 9am alone — a 35 per cent jump.

Local traffic is also expected to reduce, following the success of the Metro in the city and North West.