LOS ANGELES (Reuters) - It had to happen sometime, but nobody expected the biggest film of all time to lose its North American box office crown this weekend to "Dear John," a low-budget "chick flick" with a pair of little-known stars.

The romantic drama opened at No. 1 with three-day sales of $32.4 million across the United States and Canada, crushing both industry forecasts and reigning champ "Avatar," according to studio estimates issued on Sunday.

James Cameron's 3D sci-fi spectacular slipped to No. 2 with $23.6 million in its eighth weekend. But "Avatar" remained the top pick overseas, earning $76 million. Its worldwide tally rose to $2.21 billion, divided between $630.1 million from North America and $1.58 billion from foreign markets.

"Avatar" last Tuesday surpassed the $601 million haul of Cameron's 1997 release "Titanic" to become the biggest movie of all time in North America. It had already taken the international and worldwide titles from "Titanic" thanks to ticket-price inflation and the higher cost of 3D screenings.

Pundits had forecast the 20th Century Fox release would lose its North American crown next weekend to "Valentine's Day," which will take advantage of both the eponymous holiday and the U.S. Presidents Day weekend.

But few predicted that "Dear John" would cause a stampede to movie theaters by young women. Moreover, the hardy demographic appeared to ignore the blizzard that shut down a large swathe of the mid-Atlantic region.

"When they come out, young women come out in droves," said Geoffrey Ammer, president of worldwide marketing at the film's closely held financier Relativity Media.

He said the first wave of moviegoers texted and Tweeted their friends during the screenings to deliver their favorable verdicts, triggering further waves.

MEN "KICKING AND SCREAMING"

Channing Tatum and Amanda Seyfried star as lovers whose romance is curtailed by the September 11 attacks. It was directed by Swedish filmmaker Lasse Hallstrom and based on a novel by Nicholas Sparks ("The Notebook").

The film was distributed by Sony Corp's mid-budget label Screen Gems, after Time Warner Inc's New Line Cinema unit dumped the $25 million project. Screen Gems said audiences for the film were 84 percent female and almost two-thirds were under the age of 21.

Ammer said the handful of men "dragged kicking and screaming" to the movie appeared to enjoy it, and he hoped word-of-mouth would bring in more of them. Critics largely ripped the movie.

John Travolta's latest box office offering, "From Paris With Love," was the actor's worst start in almost a decade. The crime thriller opened at No. 3 with $8.1 million. Distributor Lionsgate had hoped for an opening in the mid-teen millions, and said the blizzard did not help business. Critics were also unkind.

Travolta's previous worst opening was the $4.5 million start for "Lucky Numbers" in October 2000. He was in theaters last November with "Old Dogs," which opened at ticket sales of $17 million.

"From Paris With Love" was made by French filmmaker Luc Besson's Europa Corp, which enjoyed a worldwide hit last year with the Liam Neeson kidnap thriller "Taken." Pierre Morel directed both films. Lionsgate is a unit of Lions Gate Entertainment Corp.

Also new to the top 10 was Fox Searchlight's "Crazy Heart," which expanded nationally after seven weekends in limited release on the heels of its three Oscar nominations on Tuesday.

The picture earned $3.65 million, jumping six places to No. 8. Its total stands at $11.2 million. Jeff Bridges, its star, is considered the favorite to take home the best actor Oscar on March 7 for his role as a washed-up country music singer and songwriter. Fox Searchlight and 20th Century Fox are units of News Corp.

"Avatar" and "The Hurt Locker," the latter now out on DVD, led the Oscar field with nine nominations each.

(Reporting by Dean Goodman; Editing by Cynthia Osterman)