Sydney - In Yoko Ono's new exhibition "War is Over (if you want it)" in Australia, the writer, artist and peace activist hopes to unite people to dream and work towards a better future through art.

"It's what we can do to change society," Ono, the widow of Beatles frontman John Lennon, told a news conference at the Museum of Contemporary Art Australia in Sydney, where the show opens on Friday and runs until late February.

The interactive parts of the exhibition were designed to encourage collaboration between people, linked to a central theme of world peace, she said.

The mixed-media presentation, Ono's first solo show in Australia, features works from more than five decades including sculptures, vintage collage spreads and a chess game with all-white pieces.

The title "War is Over (if you want it)" refers to a campaign by Ono and Lennon in 1969 when they rented billboards in various cities to display a message of peace over Christmas. "Change is not that easy but we have to understand that if we don't allow change, that is death," Ono said.

A prolific user of Twitter, Ono tweeted against gun violence this year and posted a photograph of the blood-stained glasses that apparently were worn by Lennon when he was shot to death in New York in December 1980.

"When John and I stood up, very few people were activists. Now I think 90 per cent of the world is activists," she said. "If you're not an activist, you'd be considered a nerd maybe."