TOKYO (Reuters Life!) - Hollywood star Will Smith had the producer of his latest film holding his head in anguish on Tuesday after the actor gave away the ending of "I Am Legend."

Speaking at a Tokyo news conference, Smith inadvertently revealed the plot, prompting co-producer and co-screenwriter Akiva Goldsman to shout: "Don't give away the ending!"

Goldsman then pretended to be surprised, but it was all too late, and press handlers asked all present to keep the ending a secret, so as not to spoil it for viewers.

Smith plays a virologist fighting a man-made virus in "I Am Legend," the film adaptation of Richard Matheson's 1954 novel of the same title.

The movie premieres simultaneously in the United States and Japan on December 14.