Actors in the US have thrown their weight behind their striking Australian counterparts.
The Screen Actors Guild of America is advising its members not to accept work on Australian productions without seeking permission from the Media, Entertainment and Arts Alliance (MEAA).
The Australian MEAA union is seeking better pay for its members and a greater share of profits.
Stars of series such as Neighbours, Home and Away and Blue Heelers have staged one 24-hour walk-out, with more expected if a deadline of 23 July is not met for agreement.
Among those lending their support to the strike were present and former Neighbours cast members including Jason Donavan, Brooke Satchwell, Tom Oliver and Alan Fletcher.
Writing to the MEAA, the SAG said it supported the Alliance in its fight for "a fair and just agreement covering theatrical motion pictures and television productions".
Canadian unions have also urged members not to sign up to Australian productions.
The Screen Producers Association of Australia (SPAA) said it cannot afford to increase pay by setting a minimum weekly wage because it does not get the same high production budgets as US TV series.
The average Australian actor earns about A$10,000 (£4,100) per year.
The union said some cast members are told by a show to keep a whole week free but have all of their scenes squeezed into one day.
They then get paid for only that day.
The SPAA said the strike could disrupt shooting schedules and cost about A$140,000 (£57,500) in lost revenue.
Negotiations have been going on for eight months and progress has been made on the issues of nudity and smoking.