Chris Hemsworth arrives at "The Avengers" premiere on April 11, 2012 in Hollywood. Credit: Jon Kopaloff/FilmMagic

Chris Hemsworth can't wait to welcome his firstborn with wife Elsa Pataky -- but he's not one to gush about the experience.

When E! News asked The Avengers actor if they're expecting a boy or a girl, the cheeky Aussie responded: "It's definitely one of them! It's a secret."

Hemsworth, 28, added that he's received plenty of parenting tips from friends and family since announcing their baby news in January. "People, as they give you advice, they end with: 'By the way, nothing will prepare you, so good luck!'" he laughed.

Married since December 2010, Hemsworth and his Spanish actress wife, 35, are "beyond thrilled to have this baby," a source close to the two stars tells Us Weekly. "They're an adorable couple."

For now, Hemsworth's thoughts are consumed by his role as Thor in The Avengers. "I was with the character for two or three years. It's all blended into one period," said the actor, who donned a three-piece John Varvatos suit. "We start shooting [Thor 2] in a couple of months. I shot a couple of things in between, but it feels like it sort of rules my life at the moment."