Robert Downey Jr. has confirmed the gender of his baby.

The actor was on The Tonight Show with Jay Leno when he revealed his happy news.

After struggling for a few minutes about whether he should make the news public, he covered his face in his hands and announced, "We're having a boy".

Robert and his wife producer Susan Downey have been married for six years and are expecting their first child together in February.

Robert has an 18-year-old son, Indio Falconer, from his previous marriage to Deborah Falconer.

The star is currently promoting his new movie Sherlock Holmes: A Game of Shadows. He has reprised his role as the title super sleuth, while Jude Law plays his sidekick Dr. Watson.

The 46-year-old recently said that he wouldn't be able to take time off to welcome his new arrival.

Robert is looking forward to the birth of his baby, but he has already got a packed schedule.

"Life is good," he told Live magazine. "With a new baby on the way, maybe I ought to think about slowing down a little. But I can't see that happening in the short term."