ADELAIDE, Australia - Lance Armstrong's countdown toward retirement will reach a significant marker Sunday when he begins his last race outside the United States.

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The seven-time Tour de France winner will ride in a criterium prologue to the Tour Down Under, and when the race ends seven days later and after 750km (500 miles) around South Australia, the end of his celebrated career will loom larger.

The 39-year-old Armstrong reflected upon his career on Saturday, saying the comeback he began in the same race three years ago had not lived up to his expectations "but that's what happens in sport."