Action flick "Transformers: Dark of the Moon" opened to $13.5 million at box offices in its late night and midnight screenings in the United States and Canada, according to studio estimates released on Wednesday.

The 3-D film based on toys from the 1980s saw its debut night box office figures come in below the last movie in the series, 2009's "Transformers: Revenge of the Fallen" which opened to $16.6 million in midnight screenings.

But with the July 4 weekend approaching, the film is expected to earn between $150 million and $180 million over its first six days in the U.S. and Canada, said Paul Dergarabedian, president of Hollywood.com Box Office.

"Transformers: Dark of the Moon," with its big action and special effects, is widely expected to be among the biggest blockbusters of the summer.

It opened in 3,000 U.S. and Canada locations in screenings late on Tuesday and at midnight, and through Monday it will play in over 4,000 locations, Dergarabedian said.

The movie franchise revolves around Autobot robots who battle their foes the Decepticons. Both factions transform themselves into vehicles and other types of machines.

In the latest movie, the 1960s U.S. mission to the moon uncovers an Autobot and a mysterious spaceship, which leads to a showdown between the two sides of robot warriors.

Critics are divided about the film, which has earned only a 37 percent positive ranking on review aggregating website Rotten Tomatoes.

While that may seem low compared to other films, the last movie in the series stands at 20 percent on the site.

Critic Alonso Duralde of website The Wrap wrote, "For all the bombast, alas, 'Dark of the Moon' remains a joyless and decidedly impotent exercise that all the metaphorical rocket launchers and bazookas in the world can't fix."

But Los Angeles Times critic Betsy Sharkey said, compared to the last "Transformers" movie, director Michael Bay delivers a "leaner, meaner, cleaner 3-D rage against the machines."

Dergarabedian said the $13.5 million opening "still shows a lot of interest" for the film from Paramount Pictures, a unit of Viacom Inc.

"I don't think it's anything to cry about, they're going to be fine," he said.

In fact, Dergarabedian estimated that worldwide the movie could earn about $500 million in its first six days.

Last year, vampire romance movie "The Twilight Saga: Eclipse" earned a record-setting $30 million in midnight showings on a Wednesday, Dergarabedian said.

"Transformers: Dark of the Moon" stars Shia LaBeouf and Rosie Huntington-Whiteley, a former lingerie model who replaced actress Megan Fox in the third film in the "Transformers" franchise.