JK Rowling said she was in a "bleak mood" travelling to America on Wednesday but refused to speak about Donald Trump as she promoted Harry Potter prequel, Fantastic Beasts And Where To Find Them.
The author, who has been a vocal critic of the president-elect, said she wanted to "focus on some good things" as she attended a press conference for the film in New York.
But she revealed the story of Fantastic Beasts was partly inspired by "the rise of populism" around the world.
"I think today is a day to focus on some good things and putting some good things out into the world hopefully," JK said.
"If you have read the Potter books, you'll know this period of history threatened to become very dystopian. You were looking at the rise of a very dark force.
"I conceived of this story a few years ago. It was partly informed by what I see as a rise of populism around the world."
She added: "Last night I was in a kind of a bleak mood boarding the plane and I thought I need to work.
"I got out the second screenplay and worked on that and it made me feel a whole lot better."
It has been reported that a sequel to Fantastic Beasts may feature a gay relationship between the character Grindelwald, played by Johnny Depp, and a young Professor Dumbledore from the original Harry Potter stories.
Addressing the speculation, JK said: "I can't tell you everything I'd like to say because obviously it's a five-part story and there's lots to unpack in that relationship.
"I will say you'll see Dumbledore as a younger man and quite a troubled man because he wasn't always the sage. He was always very clever.
"We'll see him at what I think was the formative period of his life. As far as his sexuality is concerned, watch this space."
JK, who is working on a new novel and a screenplay for the Fantastic Beasts sequel, said she would feel strange if she stopped writing despite amassing a vast wealth.
"Clearly I don't need to write any more," she said. "I love it so much it would feel like, almost some of psychic amputation If I didn't write."
JK also revealed she hoped to bring the West End play Harry Potter And The Cursed Child to Broadway but there were currently no plans for a stage version of Fantastic Beasts.
"Let us do the movies first," she said.
Eddie Redmayne, who plays the lead role of Newt Scamander, said he was in "shock" when Rowling announced there would five films in the series.
"So much about this process has been top secret that it was secret to us," he said.
"Our scripts were put in safes at the end of the day, but all for a reason we understand, which is there's such an appetite for the world and the universe and the stories that Jo creates.
"In this world of so few surprises, it's wonderful to try and keep those secrets.
"When you announced it was five, it was absolutely a shock to us. It was shocking and very exciting at the same time."
The world premiere of Fantastic Beasts And Where To Find Them will take place at Alice Tully Hall at the Lincoln Centre in New York City on Thursday evening. The film is released in UK cinemas on November 18.