Lance Armstrong has thrown his support behind his fellow American Floyd Landis, who plans to make a comeback to cycling next month after serving a two-year ban for doping.

Armstrong said Landis, who was stripped of his victory in the 2006 Tour de France when he tested positive for synthetic testosterone, deserved a second chance.

"People serve their time, just like everybody else and when their time is up, they get to go back to work," Armstrong told reporters at the Tour Down Under in Australia on Friday.

"Let's forgive, forget and get down the road."

Landis has denied wrongdoing and launched a series of legal challenges against his ban, which ends next week.

The 33-year-old plans to make his comeback in the Tour of California, where Armstrong will also be riding.

"You've got to remember, Floyd might have been found guilty, but at the end of the trial if you polled the people, more than 50 per cent thought he was innocent," Armstrong said.

"In regards to that, it's good that he's back."

COMEBACK RACE

Armstrong, a record seven-times Tour de France winner, continued his own comeback on Friday, finishing the fourth stage of the Tour Down Under in 47th position to climb one spot to 38th overall.

Australian Allan Davis won the 143 kilometre stage in a sprint finish to hold a narrow four second lead with two stages of the 800-kilometre race remaining.

Graeme Brown, also of Australia, finished second to remain second overall.

Armstrong, 37, has been content to ride conservatively in his first race back since he won the 2005 Tour de France but said he might make a charge on Saturday.

"I think I can be there, I know I won't be riding away (from the field)," Armstrong said. "I'm sure they will open up the race tomorrow.

"These guys are strong and again, it depends a little on the wind ... if it's a headwind like it was in training, it will be hard for anybody to ride away."