U.S. pop star Justin Timberlake said he is planning to write a song for his friend Ellen DeGeneres and her new bride Portia De Rossi.

"I actually made them a promise and I'm gonna stick to it," Timberlake said when he called into radio's "The Billy Bush Show" Thursday.

Asked if there is any truth to rumors his former boy band N'SYNC is planning a reunion, Timberlake told Bush: "We haven't talked about it. There's nothing in the works for that."

One artist he may be collaborating with, though, is Beyonce.

"We are still in the process of creating, but we've been in the studio a little bit and just writing and producing some songs for her," he said.