Sigourney, who has so far starred in four films in the series, told the crowd at the Hero Complex Film Festival that she was convinced there was still room for more after meeting fans of the films - "so passionate about the series, passionate about Ripley. There's more story to tell, but I don't know how to do that."
The actress expressed her fears of where the story could go, though.
"I don't think Alien belongs on Earth popping out of a haystack, which is where I was afraid it was going to go," she told the audience. "I feel it should take place in the far reaches of the universe where no one in their right mind would go. There are very few filmmakers that I can think of that I would want to entrust this to."
Do you want to see a new Alien film? Share your thoughts below...
The original film, came out in 1979, with Sigourney rewriting the template for female action heroine, all sinewed muscle and guts, taking on, single-handedly, the ruthless Alien, after the demise of her colleagues one by one - including, painfully, John Hurt.
"If you just read the script, it's basically just 'Ten Little Indians' and the monster is just — some monster," said Sigourney.
"I pictured this big blob of yellow gel rumbling around."
She said she realised the importance of her character, though, for fans around the world...
"People have a connection with her because of her moral compass and because somehow she's so consistent. She can't help but want to preserve humanity … I think that's something that just reaches out to people. That she's someone you could count on when you're in a jam.
"She has some sort of steel thread running through her that's not going to give up that I find, as an audience member, very interesting."