Nik Wallenda, the Florida-based daredevil, acrobat and heir to the famed Flying Wallendas circus family legacy, is afraid of only one thing.

“I would say the only thing I fear is God,” Wallenda, 34, said.

He certainly had no fear of walking across Niagara Falls on a tightrope, riding a bike on a high wire 260 feet above the ground or hanging from a hovering helicopter by his teeth.

On Sunday, Wallenda will attempt an even more ambitious feat, even for a man who was born into a family of risk-takers.

He will walk on a tightrope stretched across the Little Colorado River Gorge near the Grand Canyon. The event, which will be broadcast live (with a 10-second delay) at 8 p.m. EDT, will take place on the Navajo reservation near Cameron, outside the boundaries of Grand Canyon National Park.

Wallenda will walk a third of a mile across a wire suspended 1,500 feet above the river. (In comparison, the Empire State Building in New York City is 1,454 feet high).

“I respect deeply what I do and realize there’s a lot of danger in it,” he acknowledged on a recent day in his Florida hometown of Sarasota.

Wallenda, who is married and has three children, always says a prayer with his family prior to stepping onto the wire.

Wallenda was born a year after his great-grandfather died and began wire walking at the age of 2, on a stretched rope 2 feet off the ground. He grew up performing with his family and as a teen, had an epiphany.

“It’s an honor to be carrying on a tradition that my family started over 200 years ago,” Wallenda said during a recent news conference in Florida. “When I turned 19, I told my family I was going to set out to make sure everyone in the world knew who the Wallendas were again.”

Over the years, Wallenda has performed some dangerous stunts, but his walk across Niagara Falls in June 2012 placed him firmly in celebrity territory.

Wallenda became the first person to walk on a tightrope across the mist-fogged brink of the falls separating the U.S. and Canada.

Other daredevils had wire-walked over the Niagara River, but farther downstream and not since 1896.

Niagara Falls, Wallenda said, was a dream of his. So is the Grand Canyon.

But here’s the difference between the two stunts: ABC televised the Niagara Falls walk and insisted Wallenda use a tether to keep him from falling in to the river. Wallenda agreed to the tether.

The Discovery Channel will televise the Grand Canyon walk, but Wallenda won’t wear a tether. There won’t be a safety net, either.

Wallenda anticipates it will take him about 30 minutes to cross the chasm.

For the past two weeks, Wallenda — who has a boyish face, strawberry blonde hair and a muscular build — has been practicing in front of crowds in his hometown of Sarasota.

Each morning and evening, he glides across a 2-inch cable strung on the banks of a river. Hundreds of local fans show up every day to watch.

“I’m just fascinated by the movement, the way he walks,” said Loy Barker, a Sarasota resident who watched one of Wallenda’s practice sessions.

Wallenda has tried to simulate different conditions he might face while crossing the gorge.

“It’s very important that I train on a cable that simulates the weight, the feeling, the movement of the cable, the way it will move under my feet,” he said. “We have also brought wind machines out. I’ve walked in 52 mile an hour gusts during Tropical Storm Andrea, with a torrential downpour. And we also brought out wind machines where we simulated 45-55 mile per hour gusts. Then I also walked in 91 mile an hour winds that day.”

Only one thing could halt the planned wire walk, he says, is lightning within a 15-mile radius of the wire.