Members of US actors union Sag-Aftra and the Writers Guild of America (WGA) took part in National Day of Solidarity rallies on Tuesday.
Thousands gathered outside studios in Los Angeles, New York, and Chicago as the actors strike entered its 40th day – having begun on July 14.
The strike began after Sag-Aftra negotiations over new contracts with the Alliance of Motion Picture and Television Producers (AMPTP) broke down.
It has caused a major halt in productions and film events in both the US and the UK, with work on films including Deadpool 3 being paused.
Sheen, known for films including Apocalypse Now and The Departed, channelled his character of president Jed Bartlet from HBO show The West Wing, as he addressed those gathered outside Walt Disney studios in Burbank, California.
He encouraged union members to “stick to it like a stamp”, with their determination for new contracts with the AMPTP.
“I have been a proud member of the Screen Actors Guild… and Equity since 1961. That was the same year I got married – clearly I have a fondness for unions,” he said.
He continued: “Clearly this union has found something worth fighting for and it is very costly.
“If this were not so, we would be left to question its value. Now we are called to support the union and stand together for the long haul and stick to it like a stamp.
“The studios are always seeing what is and asking ‘why’? Let us continue to dream things that never were and say, ‘why not?’” he said.
Sheen was joined at the rally by other members of The West Wing’s creative team, as well as actor Ron Perlman.
In her own remarks, Washington, who played a government fixer on ABC political drama Scandal, said she had almost not pursued a career in acting until she learned about unions.
“I learned that there are communities of people that were making a living being working actors, I learned I didn’t have to want to be famous, I could just pursue a career doing what I loved to do and I could raise a family and live a life doing that, being paid a fair wage,” she said.
“We have come to a point in our history where that is no longer possible, where just being a working actor… means I can’t make a fair living. It’s not ok.
“It’s not ok for other people to benefit for our hard work and sweat, when we work 16-hour days, when we put our vulnerabilities and hearts on the line, while we do the hard work, that’s not ok.
We deserve to be paid a fair wage, we deserve to be able to have access to healthcare, we deserve to be protected from machines pretending to be us, we deserve to be working artists and to be paid fairly.
“The dream of being a working artist should not be impossible.”
Picket lines were cancelled on Monday in Los Angeles due to tropical storm Hurricane Hilary and a 5.1 magnitude earthquake in the city.