AceShowbiz -

Jessica Chastain has turned down the chance to star in "Iron Man 3". The "Take Shelter" actress officially confirmed that she won't be joining Robert Downey Jr. in the third armored hero movie despite swirling report that she's in talks to play a "sexy scientist every bit as smart as Tony Stark."

"Sorry to say that 'Iron Man 3' isn't going to work out," so Chastain wrote on her Facebook page. "My schedule is jammed packed and I can't fit anything else in. The press announced my possible attachment far too soon."

The actress also offered an apology to her fans for withdrawing from the tentpole project. "I know many of you wanted me to be involved, and I'm so sorry to disappoint you," she stated. "Hopefully there'll be another Marvel in my future. [Director] Shane Black and everyone on the IM3 team are really wonderful. I'm very excited to see the film when it comes out. xx."

Before Chastian's name was mentioned in the mix, it was rumored that Marvel Studios was also lining up meetings with some other atcresses such as Diane Kruger, Gemma Arterton as well as Isla Fisher.

"Iron Man 3" is said to be loosely based on Warren Ellis' six-issue "Extremis" comic book series, which presents a new origin story that focuses on nanotechnology. The third "Iron Man" movie is planned to kick off production this month in North Carolina before continuing in China in late summer.

Aside from bringing back Downey Jr. as Stark a.k.a the titular hero, the upcoming Marvel superhero movie will have Gwyneth Paltrow and Don Cheadle returning as Pepper Potts and Rhodey respectively. Walt Disney Pictures will release the movie in the U.S. on May 3, 2013.

As for Chastain, she will next be seen starring opposite Shia LaBeouf and Tom Hardy in John Hillcoat's "Lawless (2012)", and lending her voice to Gia The Jaguar in "Madagascar 3: Europe's Most Wanted".