It's hard to believe, but even Steven Spielberg can have moments of hesitation when it comes to recruiting actors.

When ET caught up with The BFG director at the film's premiere on Tuesday, he revealed that he was apprehensive about presenting the script to Oscar-winning actor Mark Rylance.

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"When I was working with Mark the first day on Bridge of Spies, he was so not Mark Rylance," Spielberg told ET. "He so became Rudolf Abel, and there's nothing he can't do."

Despite his trepidation, Spielberg gathered up the courage to go after the British star, but not without some confusion.

"At the end of the day, I took a chance and said, 'Would you read a script?'" Spielberg recalled. "I neglected to say 'a script for you to star in.'"

"I thought he was just asking me to read an interesting script," Rylance admitted to ET. "I didn't know he was offering me the part."

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In the movie, Rylance provides the voice for the BFG (Big Friendly Giant). Based on the classic story by Roald Dahl, The BFG follows the titular character as he embarks on an adventure with a girl named Sophie. After being fearful of the BFG at first, Sophie is soon at ease when she learns that unlike the other giants, the BFG does not eat children. Together they come up with a plan to get rid of the other giants who have become increasingly bothersome.

Sophie is played by newcomer Ruby Barnhill, who Spielberg insisted is the crux of the film.

"It really came to life when Mark and Ruby stepped into their parts," he said. "That's when the movie started to live."

The BFG hits theaters July 1.