NIAGARA FALLS: As he does every time he climbs on a tightrope, Nik Wallenda will say a little prayer on Friday as he mounts the thin steel wire for what could be his greatest aerial triumph.

Perched on an impossibly narrow steel cable some 60 meters (200 feet) in the air, this scion of one of America's first families of acrobats is aiming to do something untried in more than a century, crossing the treacherous Niagara Falls on a high-wire.

If he succeeds, the achievement will add to the lore and legend of the renowned Wallenda family, famous over the decades for jaw-dropping stunts executed from dizzying heights.

Wallenda says this coming challenge which will be watched live by his three children will be his greatest feat yet.

“It's been a dream of mine since I was six years old. Twenty-seven years I've been waiting and to do this, and it finally is coming true,” said Wallenda, 33, who has been walking on tightropes since the age of two.

Any attempt to cross the falls is usually strictly forbidden, but an exception was made for Wallenda, who is descended from a long line of acrobats and circus performers.

Wallenda estimates that it should take about 40 minutes to cross from one side of the falls to the other, along the 550-meter (1,800 foot) metal cable on which his life hangs.

Aided by a balancing pole, he will begin his crossing on the American side of the falls, slowly walking to Canada and guaranteed acclaim.

Friday's attempted Niagara crossing is expected to draw thousands of anxious spectators, all glued to his first careful steps.

For the task, Wallenda will be wearing a pair of shoes custom-made in supple leather by his mother.

“They are almost like Indian moccasins with a suede leather bottom the leather is there to protect my feet from getting bruised by the cable and so that I can feel the wire,” Wallenda said.

The “Flying Wallendas” have soared, cantered or ever-so-carefully tiptoed over the heads of mesmerized audiences for seven generations.

The Wallenda name for generations has been the stuff of legend, astonishing audiences first in Europe, then in the United States with their aerial acrobatics.

Their fame really took off in 1978, when they were made the subject of popular made-for-TV movie, “The Great Wallendas.”But their name is also synonymous with tragedy. Several family members over the years have lost their lives attempting dangerous routines.

“I never wore one my in my life or in my entire career,” Wallenda told AFP.

“I am not excited about it, but I really don't have a choice unfortunately.”In addition to the harness, Wallenda's best protection will be the weeks of relentless training he has put in.

“We set up a cable practically the same distance as well as the same tension as when I'll be walking over Niagara Falls,” he said.

“We also simulated high winds, winds up to 55 miles (90 kilometers) per hour, and a heavy, heavy mist, so I'll be prepared for whatever I face.”But nothing can fully prepare someone for the vagaries of wind and the crashing waters of the tempestuous falls, said to be one of the world's most imposing natural wonders.

“It adds a lot of challenges, not only as the cable will be moving, but there is heavy mist in the air, there can be high winds from multiple directions,” Wallenda told AFP.

Still he said, such variables are “all things I've been preparing for, and that's why we trained the way that we did, simulating those worst-case scenarios.”The challenge is particularly difficult because the steel cable, weighing several tons, is somewhat slack, meaning he will likely bob and bounce as he carefully traverses the rushing waters below.

Wallenda is already listed twice in the Guinness Book of World Records for high-wire acts while simultaneously cycling.