The vote started yesterday at 7.30pm PT at a meeting near Universal Studios in Hollywood, California.
The meeting is one of three WGA is planning in relation to its negotiations with the Alliance of Motion Picture and Television Producers, which are due to restart on April 25.
A second round of talks were suspended last week. Should a new deal between the pair not materialise by May 2 and the WGA votes to ratify a strike, work on many programmes and films will stop on that date.
The matter centres on what the WGA claims are increasing poor levels of pay, primarily due to networks moving towards shorter runs and trying out smaller writing team models for some shows. There are several other issues on the table too.
The last time writers on the East and West Coasts voted to strike, the US entertainment business was virtually shuttered over night and didn’t start up again for nearly 100 days.