Lance Armstrong trades pedal power for pavement-pounding Sunday in the New York Marathon, but the seven-time Tour de France winner holds no illusions about winning his debut at the distance.

The 35-year-old American has not run beyond 16 miles at a time in practice but is confident he can finish the 26.2-mile journey in about three hours.

"I have been able to average six-minute miles for 10 miles but they say the 20-mile mark is just halfway," Armstrong told USA Today.

"I have no delusions of grandeur about my finish. It's too late for any crazy marathon training. It's just too much pain. That might be the nail in the coffin. I can't see doing another marathon but I'll always be a runner."

Armstrong reached the 10th anniversary of being diagnosed with cancer this past October 2 and will wear runner number 1002 - for 10-2 - on Sunday.

Injuries have nagged Armstrong during training. Painful shin splints have limited the former triathlete's ability to prepare for the race.

But Armstrong has received help from Kristin Richards, his former wife, who began marathons after their 2003 divorce. While she will not run here, Richards raced at last year's Chicago marathon and this year's Boston marathon.

"It's kind of funny that she's giving me tips," Armstrong told USA Today. "I listen to Kristin. I listen to her a lot more than people may think. We have a very good relationship."

Armstrong will go from wearing the yellow jersey among the peloton riders in climbs up the mountains of France to pounding the pavement in a pack of 40,000 runners.

Chris Carmichael, Armstrong's long-time cycling coach, supported Armstrong's training and nutrition needs and the transition in preparation styles from cycling to running.