Helena Bonham Carter is in negotiations to appear in McG’s upcoming action flick “Terminator Salvation,” the fourth installment in the popular series launched by James Cameron in 1984.

According to The Hollywood Reporter, Carter’s role would be small but crucial to the story. The film stars Christian Bale in the role of lead character John Connor, who struggles to prevent the ruthless machines from eradicating humanity.

Anton Yelchin, Sam Worthington, Moon Bloodgood and Bryce Dallas Howard co-star. “Terminator Salvation: The Future Begins” already started principal photography, with a release date set for May 22, 2009. A potential SAG strike could however cause delays in the production.

Bonham Carter was last seen alongside Johnny Depp in “Sweeney Todd: The Demon Barber of Fleet Street.” She will next reprise her role as Bellatrix Lestrange in “Harry Potter and the Half-Blood Prince.”

Although she’s supposed to make a brief appearance only, her addition to the cast of the new “Terminator” sequel is quite an exciting surprise. Now that he has an A-list cast ready to battle the machines, McG better not mess this thing up.