His promoter has been quoted in international media as saying that the Filipino will get into the ring with Horn on April 22.
Pacquiao's promoter, Bob Arum has been widely quoted in international media as saying that the Filipino dubbed "Pac-Man" will get into the ring with 28-year-old Horn on April 22.
But Pacquiao's spokesman told AFP the match still has to be confirmed.
"We don't have confirmation on that yet because we are still going to discuss that with Bob Arum," the spokesman quoted Pacquiao as saying in response to the reports.
Pacquiao, 38, has previously parlayed his sporting fame into a career in politics, getting elected to the influential Philippine Senate last year while still continuing to box professionally.
A veteran of 67 fights with 59 victories, his record easily dwarfs that of Horn who has notched up only 17 fights with 16 wins.
In his last fight in November, Pacquiao reclaimed the World Boxing Organization welterweight title for the third time with a unanimous-decision victory over former champion Jesse Vargas in Las Vegas.
The Filipino southpaw had briefly retired from the ring after beating American Tim Bradley in Las Vegas in April but was soon back in the ring, saying he still felt like a youngster.
He has made repeated calls for a rematch with American rival Floyd Mayweather who defeated him in a long-awaited showdown in May 2015.
However Mayweather, who retired in September of that year, has refused to take the bait.