The 25-year-old time trial specialist said he is targeting the team time trial with BMC and the individual time trial for his home country, and he won't have the training in his legs to perform well in a 259.2km road race.
"I got a letter from the Australian selectors, Bradley McGee, to be more specific, and it just asked what our race program and what our progression is leading up to Worlds and what our thoughts were," he said after stage 2 of the USA Pro Challenge, where he is currently second overall behind teammate Brent Bookwalter.
"I said, 'Look, my two biggest goals are the team time trial and the time trial. One, we want to win that team time trial again, and I want to win that time trial,'" he said. "For the road race I said, 'I think it’s probably not fair that I race the road race.' And the reason for that is I'm preparing for two 50km races, and that's a 250km race."
Dennis, who finished fifth in the individual time trial last year in Ponferrada, Spain, but failed to finish the road race, said he doesn't believe he'd be much help for the Australian team's chances in this year's road race on September 27.
"The race probably starts after four hours in reality, and I'd be gone by then, just like last year," he said. "My body wouldn't be used to it and I wouldn't have the kilometres in my legs, so I'd be dead after three-and-a-half, four hours, for sure.
"I questioned whether or not I should actually be in that road race and if there's a job early on that I could do, that there is maybe someone else who could do it as well and then still help in the finish."
The Australian team for the World Championships, including reserves, will be announced on September 2.