Rehan Jalali is offering to bulk up Robert Pattinson for his "Batman" role, following reports that he is having trouble building muscles.

Jalili, the author of "The Six-Pack Diet Plan," took to Twitter to offer his services to "Batman" director Matt Reeves and to Pattinson. He assured that he can get the "Twilight" alum to bulk up just as he helped Affleck in the past.

Jalili shared an article from Livestrong that detailed how Affleck gained 24 pounds of muscle for his "Batman" role in Zack Snyder's film. The actor strictly followed the fitness trainer's "Six-Pack Diet Plan." which had him eating six to seven small meals every day.

The diet required 45 percent complex carbs such as rice, broccoli, and sweet potatoes and 35 percent lean protein including egg whites, lean steak, and chicken breast. The remaining 20 percent is for essential fats like almonds and flaxseed oil.

The celebrity fitness trainer said he can give nutrition and fitness advice for Super Hero Body building when asked if he has already started bulking up Pattinson.

Not working with him yet but here to offer any nutrition and fitness advice for Super Hero Body building! 💪🏼

— Rehan Jalali (@SixPackDietPlan) December 18, 2019

Reeves and Pattinson have yet to respond to Jalili's offer. But his tweet is in response to rumours that the 33-year-old English actor is having trouble building muscles. The problem has reportedly caused production delays for at least a couple of weeks.

Pattinson naturally has a slender build so it may take lots of exercises and a proper diet to get him jacked up. Likewise, it was just in October that he revealed that he is in the "very very early stages" of bulking up for "Batman" so it takes time.

In an interview for his recent movie "Lighthouse," Pattinson shared that he does not like to exercise. But he got around to doing it eventually because he realised that he is getting older.

"I didn't when I was younger, but now as I have kind of gotten older, I'm slowly getting aware of aging. So I'm kind of like, 'I got to put in some effort otherwise I'm going to get hip replacement,'" Pattinson said in the video below.

Q: are you starting to buff up for Batman?

Rob: "I'm early stages, very very early."

— ibabysky (@Ibabysky) October 20, 2019

Filming for Reeves' "Batman" is set to begin early next year. The film is expected to hit theatres on June 25, 2021.

Robert Pattinson
Robert Pattinson attends the Closing Night Screening of 'The Lost City Of Z' for the 54th New York Film Festival at Alice Tully Hall, Lincoln Center Jamie McCarthy / Getty