The move comes shortly after Stewart, 22, publicly confirmed and apologized for cheating on Pattinson, 26, with Rupert Sanders, the married 41-year-old director of her film "Snow White and the Huntsman."
"I'm not sure they'll be able to recover from this," a source told People.com Thursday, adding Pattinson "is heartbroken and angry" because of Stewart's actions.
The couple, who co-star in the "Twilight" film franchise, have been dating about three years.
Blunt and McGregor previously worked together on the 2011 film "Salmon Fishing in the Yemen."
Jim Bell, the executive producer of NBC's coverage of the games, announced the stars' participation in NBC coverage of Friday's 4 1/2-hour Olympics opening ceremony during a teleconference with journalists Thursday, EW.com reported.
"It is pretty breathtaking," Bell said.
"I think it will give you a sense of the flavor of our coverage and the feeling we're all having going into these games," EW.com said Bell added.
"Having seen it ... I can tell you that it includes some amazing moments, including one that I think will be among the most astonishing and memorable in opening-ceremony history, and one that people will be talking about for years to come."
"Katie," an hourlong, nationally syndicated program, is to be taped in New York and will debut Sept. 10. Each episode will be introduced with "This Day," a song Crow performed especially for the show. The Grammy Award-winning artist composed the theme with longtime collaborator Jeff Trott.
"Katie is somebody I can talk to about the things so many of us juggle: our children, careers, health, and balancing our personal and professional lives. Plus, she is really fun! I think her show will reflect the same kind of heart and energy I try to give my music, so 'This Day' was a fun project to work on together, as friends," Crow said.
'GANGSTER SQUAD:' Warner Bros. has delayed the release of its film "Gangster Squad" to 2013 in light of last week's mass shooting at a Colorado movie theater.
It was set for release Sept. 7, but was pushed back to next year after a 24-year-old man allegedly opened fire in a packed screening of the studio's latest Batman flick "The Dark Knight Rises" in Aurora, Colo., killing 12 people and wounding dozens of others, The Hollywood Reporter said.
Right after the screening in Aurora, Warner Bros. pulled theatrical trailers for "Gangster Squad" -- which featured bad guys firing machine guns at people seated in a movie theater -- the entertainment industry trade newspaper said, adding director Ruben Fleischer is now reworking the scene.
No new release date for the film has been set yet.