Robert Pattinson and Kristen Stewart are in a relationship, "Twilight" director Catherine Hardwicke has confirmed.

Despite previously denying they are a couple, the director – who helmed the first movie in ‘The Twilight Saga’, in which the pair play lovers – insists persistent rumors they are enjoying an off-screen romance are true.

Recalling a conversation she had with 19-year-old Kristen, Catherine told Time magazine: "I didn't have a camera in the hotel room. I cannot say. In terms of what Kristen told me directly, it didn't happen on the first movie. Nothing crossed the line while on the first film.

"I think it took a long time for Kristen to realize, ‘OK, I've got to give this a go and really try to be with this person.’ "

Catherine also admitted she initially warned Robert, now 23, about trying to pursue a romance with his co-star after realizing the British actor – who plays vampire Edward Cullen in the franchise – was attracted to Kristen.

She added: "After I cast him, I told Robert, don't even think about having a romance with her . . . She's under 18. You will be arrested."

However, Catherine – who worked on the first ‘Twilight’ film – did not direct on sequels ‘New Moon’ or ‘Eclipse’, so there is doubt over how much insight into their relationship she would have.