Wallenda said Monday that ABC is adamant about making him wear the safety device out of consideration for viewers who tune in to the network's three-hour, prime-time special on June 15.
"It seems as though that's what I'm going to be doing," he told The Associated Press as he prepared to walk a practice wire outside the Seneca Niagara Casino, where a fire truck sprayed water and a jet boat motor served as a powerful fan to simulate the mist and wind that occurs as water rushes over Niagara Falls to the rocky gorge below.
"I'm upset. I'm not used to it," he said. "I've never worn a tether before so it's just something else I have to contend with when I'm out there."
Daredevils routinely used to make tightrope walks over the Niagara River gorge, downstream of the falls, until the practice was banned. Nik Wallenda's stunt will be the first attempted walk over the falls themselves.
ABC spokesman Jeffrey Schneider said the network has said all along that safety measures would be in place during the live broadcast.
"We've been saying from the start that we were going to try to have every safety measure in place to make it an exciting and thrilling walk, something that would be safe and comfortable for parents to watch with their kids," he said.
Wallenda has been practicing on a two-inch cable at the casino in front of crowds of onlookers since May 12. His final two practices were planned for Tuesday.
Wallenda is a seventh-generation member of the famous daredevil family the Great Wallendas. His great-grandfather, Karl, fell to his death in a tightrope walk in Puerto Rico at age 78.