SYDNEY ? British pop star Robbie Williams caused a stir in Australia with an on-air proposal to his US actress girlfriend during a Sydney radio show.

Williams, in Australia as he pursues his comeback, popped the question to steady partner Ayda Field during a Friday appearance on breakfast radio, after host Jackie O told him Sydney was notorious for celebrity proposals.

"Is there anyone you want to get married to?" Williams laughed.

"This is so awkward," Field replied.

"Will you marry me?" he asked.

She responded: "Yes I'll marry you," before jokingly asking him where her ring was. Williams borrowed a ring from the Australian host and slipped it on Field's finger as he repeated his proposal.

"Ayda Field, I love you so much. Would you mind being my betrothed until the end of time?"

Scores of excited fans called the station to offer their congratulations, and his official site was inundated with questions about the pending nuptials.

But Williams' London-based spokesman reportedly denied Williams was serious. "He did say it, but in a jocular manner. They are not engaged," the spokesman said, according to the public broadcaster, ABC.

Speaking on air ahead of the engagement drama, Field, 30, said she met Williams through friends and they were set up on a blind date.

She said she knew instantly that it was love, but Williams was less convinced.

"Actually I didn't like you. For the first 20 minutes I thought 'who's this mentalist?'" he said.

"I was just going to offload [her] and go home but then I fell in love instead."

Williams blamed his last major tour for landing him in rehab and prompting a three-year career hiatus, during which he grew a bushy beard and developed an interest in UFOs.

He ruled out any quick return to major touring this week, warning he would always be vulnerable to drugs.

The 35-year-old former wildman is traveling with Field, and said the pair has picked out baby names: Sonny for a boy or Sunny for a girl.