Luke Bryan is going to buy "fishing rods" for Carrie Underwood's baby.

Luke Bryan

Luke Bryan

The 42-year-old country singer is thrilled the 35-year-old singer and her husband Mike Fisher - who already have three-year-old Isaiah together - are expecting another child and he's already planned what he'll send as a gift for the new addition to their family.

Speaking to 'Entertainment Tonight' after learning Carrie was pregnant, Luke said "Oh that's news to me, that she's pregnant. I'm very, very happy for them!

"Well I'm gonna send them some fishing rods."

The 'American Idol' judge - who has sons Bo, 10, and Tate, eight, with wife Caroline Boyer - has developed a strong friendship with Mike and, after bonding with his own boys while fishing, he wants the 38-year-old hockey player to enjoy doing the same.

He said: "He has the guy that built his lake, and my fish guy, we're all kinds of linked.

"Mike's building a pond, I built a pond, that's our big connection... because we have little boys, and little boys have to have somewhere to go fishing."

Last week it was revealed Carrie can't wait to add to her brood even though she is really busy promoting her latest album 'Cry Pretty'.

A source said: "She is as excited about the baby as [her new music]. The machine that is Carrie is fully on. She's in full album mode."

The 'House that Built Me' star's three-year-old son is already bonding with his unborn sibling.

When asked if Isaiah is aware he's about to become a big brother, Carrie shared: "I don't think for real he does. He'll be really sweet and talk to my belly and kiss my belly. He's the sweetest little boy. I mean, no kid can really know that their life is going to change. He'll just have to share mommy."