Brooks & DunnCountry music's elite who gathered in Las Vegas for last night's ACM Awards are sticking around for an extra day to pay homage to retiring duo Brooks & Dunn.

With the pair announcing they'll go their separate ways following their 47-city tour called The Last Rodeo, ending a 20-year collaboration that resulted in the top-selling country duo of all time, Kix Brooks and Ronnie Dunn are being honored Monday night at the taping of 'ACM Presents: Brooks & Dunn -- The Last Rodeo.'

Although just which B&D songs have been chosen for Monday night's performances generally are closely guarded secrets, repeat Entertainer of the Year Carrie Underwood says her pick originally came out when she was eight years old. "I'm sorry they're leaving," she says of her Nashville-area neighbors.

Sugarland also will be among the performers and lead singer Jennifer Nettles has spilled the beans that they'll be singing 'Red Dirt Road,' written by their former partners on the road.

"This was our first full tour that we had gone on with another artist and being able to hear that song every night holds something special," she says.

Partner Kristian Bush adds that they will be "singing for two people who absolutely should be honored and celebrated.''

Sugarland snapped Brooks & Dunn's dominance of the Academy's Duo of the Year honors last year. B&D took it back on Sunday, adding No. 27 to their record number of ACM awards, including Entertainer of the Year three times.

Other artists set to perform on the tribute include Kenny Chesney, Taylor Swift, Jason Aldean, Rascal Flatts, George Strait, Reba McEntire and Keith Urban.

Charles Kelley of this year's multiple award-winning group Lady Antebellum, which also will perform, added to the verbal tributes: "We want to be doing what Brooks & Dunn are doing. Twenty years from now we want to say it's time to take a break."

Miranda Lambert, another multiple winner on Sunday, questioned whether the split would be permanent.

"I love Brooks & Dunn. Always have. I think they're going to be back. They can't stay away from it. Music is in their blood."

Kix added a little fuel to the speculative fire during Sunday's awards telecast with a reference to the on-again-off-again quarterback for the Jets and the Vikings. "We are currently in therapy with Brett Favre trying to figure out how to waffle on this,'' he joked.

'ACM Presents: Brooks & Dunn -- The Last Rodeo.' will be taped in the MGM Grand Garden Arena in Las Vegas where Sunday's awards show originated and will be telecast May 23 on CBS.