Sources say the move is a response to Disney shifting its Marvel mega movie, Avengers: Infinity War, from May 4 to April 27, which would have given Warners’ pic, made by sister arm New Line Cinema, only a week to thump its chest at the box office.

Rampage's producers wanted to preserve a two-week cushion, say insiders.

The Avengers and Rampage dominoes impact Ready Player One, Steven Spielberg’s adaptation of the Ernie Cline sci-fi novel. That film, which opens March 30, would have enjoyed three weeks as the sole tentpole in the marketplace.

Rampage, which has been testing very strongly, adapts the 1980s video game as it tells of three creatures — a monstrously transformed gorilla, crocodile and wolf — who terrorize a city and the man who must stop them.

Other films set to open April 13 include Neon's Shia LaBeouf-Stellan Skarsgard tennis drama Borg vs. McEnroe, LD Entertainment's high school volleyball film The Miracle Season, MGM and Anna Farris' Overboard remake, and the Fun Academy animated feature Sgt. Stubby: An American Hero.