Urban sent a letter thanking people for their support

The Australian country star, who won male vocalist of the year for the second year in a row, is undergoing treatment for alcohol abuse.

Kenny Chesney was named entertainer of the year at the ceremony in Nashville on Monday night.

Duo Brooks & Dunn's song Believe won three trophies.

'Ups and downs'

Ronnie Dunn read a letter from Urban in which he thanked his friends, family and wife - actress Nicole Kidman - whom he married earlier this year.

"I'm looking forward to coming home and seeing you all soon," Urban stated in the letter.

It's been like a huge emotional rollercoaster ride Kenny Chesney

Dunn added: "We love you Keith - good luck, brother."

Chesney, who went through a high-profile marriage and split with actress Renee Zellweger last year, also referred to his problems.

He said: "This year has in ways been the most emotionally satisfying year and also the most emotionally draining year of my life.

"There have been so many ups and downs, it's been like a huge emotional rollercoaster ride."

Rascal Flatts took the vocal group award, capping what singer Gary LeVox described as an "amazing year".