Kidman's wedding fear

Nicole Kidman and Keith Urban. Picture: FilmMagic

While Keith Urban has put paid to rumours of a split from Nicole Kidman, the singer revealed his famous wife had cold feet before they wed in 2006.

Performing in Sydney on Saturday night as part of his Light the Fuse tour, the rocker told fans Kidman was watching on from the audience and explained why he dedicated his hit Once in a Lifetime to the actress.

"About this time eight years ago we were about five days away from getting married," Urban, who previously credited his wife with helping him to overcome his drug addiction, told the audience.

"A few days before that my fiance and I were talking about the wedding and she was worried about getting married to me - understandably - I was trying every way I could to reassure her that I was born to be her man . . . the only thing I could do was reassure her, comfort her, be strong.

"The next day, I happened to be with a friend of mine who was a songwriter and I was telling him what happened and he said we should write about that so I wrote this song for my wife and she's here tonight."

Despite recent media reports suggesting things had turned sour for the couple, Urban went on to gush about his lady love, with whom he has two young daughters.

"In a world of so much darkness and toxicity and scary people, she is extraordinary, pure and a beautiful light. I love you with all my heart baby girl," the 46-year-old singer said of Kidman.

The Oscar winner, who was said to be enjoying the concert from a private box with her parents, was not the only famous face to make an appearance at the event. Jimmy Barnes, Jessica Mauboy and Urban's former co-judge on The Voice, Joel Madden, all came on stage at various points in the evening to duet with the country crooner.

Meanwhile, a source said Kidman had come down with a cold after a busy schedule of jet-setting across the globe in support of the critically panned Grace of Monaco.

"She's been doing a lot and is coming down with a bit of a cold like the rest of Sydney," the insider said, adding she celebrated her 47th birthday quietly with family on Friday.

But Kidman is due to be on the road again this week as she travels across the country to support her husband on the tour.

Rumours are swirling she will arrive in WA later in the week ahead of Urban's show at Perth Arena on Sunday.