The record was recently broken by Pete Kostelnick who completed the run in 42 days, 6 hours and 30 minutes, averaging 116km per day.
But Ashill says his challenge is not about beating the record but inspiring others to achieve their own goals in life.
"I will be challenging myself, both physically and mentally, but this is not my primary motive for the run," said the former international hockey player.
"I want to communicate to others that for an ordinary person to do something extraordinary, you must never be afraid to dream big."
His decision to run across America - crossing deserts, scaling mountains and passing cornfields - was made in 2015 after the death of his mother in England from pulmonary fibrosis.
He wants to raise money to support individuals and families dealing with the disease that affects five million people worldwide and of which half die within three years of diagnosis.
Ashill plans to run 50km every day, starting at 6am and ending his run between 1pm and 2pm. He plans to take a day off every week once he is well into the task. He has six pairs of running shoes with him.
Training for his daunting challenge began last year in New Zealand and Cyprus.
Last September, he ran half-marathons every day before going on to hill training in the Middle East.
"The talking is over. Let the running and mind games begin," Ashill told AUS.
"Maybe I will reach New York and decide to run all the way back to Los Angeles. Now that would be something special."
* You can follow Nick's journey and make a donation here: http://www.nickrunsamerica.com/donate-now/
