The Japan opening of the hit film "Barbie" was dealt additional setbacks as an online petition gained steam calling on Hollywood studios to disavow a grassroots marketing movement that made light of nuclear holocaust.

A Change.org petition collected more than 16,000 signatures over two days as of Thursday, demanding that Warner Bros and Universal Pictures, the studio behind the "Oppenheimer" biopic, call a halt to the "Barbenheimer" hashtag that has helped make the film a global blockbusters.

"Barbie", which stars Margot Robbie in the title role, has grossed more than $800 million in worldwide box office, while the film about nuclear scientist J. Robert Oppenheimer that opened around the same time last month has taken in more than $400 million.

Warner Bros initially latched on to fan-produced memes that depicted Robbie's Barbie with actor Cillian Murphy's Oppenheimer alongside images of nuclear blasts.

But fans were not amused in Japan, which in coming days will mark the memorials of the atomic bombings of Hiroshima and Nagasaki 78 years ago.

A #NoBarbenheimer hashtag trended online, re-posted more than 100,000 times by one measure, prompting Warner's Japan division to issue a rare public criticism of its parent company, which then followed with an apology this week.

Mitsuki Takahata, who voices Barbie in the dubbed Japanese version, posted on Instagram on Wednesday that she was dismayed upon learning of the memes and considered dropping out of a promotional event in Tokyo hyping its opening on Aug. 11.

"This incident is really, really disappointing," she posted.

The same day, the media-savvy U.S. Ambassador to Japan Rahm Emanuel posted a picture of his meeting in Tokyo with director Greta Gerwig, but the response online was chilly.

"Your post at this time will get on the nerves of many Japanese, and will further solidify their resolve to never go to see that movie," replied a poster known as tsuredzure on the X platform formerly known as Twitter.

A spokesperson for the embassy said Emanuel took his wife and daughters to see "Barbie" and that he embraces the film's message about women's empowerment.

No Japan release date has been announced for "Oppenheimer", which chronicles the creation of the atomic bomb. The film has been criticised for largely ignoring the weapon's destruction in Japan towards the end of World War Two, obliterating two major cities and accounting for more than 200,000 deaths.