Lance Armstrong challenged to race by Aussie triathlon star Chris McCormack

The disgraced former professional cyclist Lance Armstrong has responded over Twitter to a provocative call-out by two-time Ironman World Champion Chris McCormack.

McCormack 40, who also won the International Triathlon Union World Cup Series in 1997, challenged Armstrong to a one-on-one race in the Texan's hometown of Austin.

The challenge appeared to strike a note with Armstrong who responded on his Twitter timeline last night.

"Hey @MaccaNow - if you're serious then gimme a call. Let's discuss," Armstrong wrote.

The challenge made by the Australian Ironman champion was issued in a video posted on Triathlete Magazine’s website.

"I read an interview recently, where he believed he could win the Ironman world championships," McCormack said.

"I'm like `hey man, you can't go and make those sorts of statements without backing them up - so if you really think you can win the Ironman world championships, come and race me.

"Let's go to the back of Austin - you and me - no-one around and let's race."

Armstrong is unable to compete against McCormack in an official event following the lifetime ban imposed upon him by USADA last year, but the unofficial backyard challenge that the Aussie issued would not break any rules.

Armstrong has a history of success in competetive triathlons. The Texan was ranked the number-one triathlete in the 19-and-under group for the Tri-Fed/Texas (later USA Triathlon) 1987-88 competition.

Last year, before his ban, Armstrong also won two Ironman 70.3 events in Florida and Hawaii leading to the comments that McCormack responded to.

Whether or not this race goes ahead, McCormack has pledged to keep competing in professional triathlons next year.

Armstrong on the other hand cannot.