He also said he was not giving up his position as a playing coach in the Philippines' highly-competitive professional basketball league.
Asked in an interview with ABS-CBN television about a Horn fight, Pacquiao, said "not yet done, the negotiation is not yet done".
"We are still negotiating about that. Nothing is really final, the date, who is the opponent. There are a lot of offers from other countries."
Pacquiao's promoter, Bob Arum, has been widely quoted in international media as saying that the 38-year-old Filipino dubbed "Pac-Man" will get into the ring with Horn in April, possibly in Australia, but Pacquiao himself has not confirmed this.
The Philippine boxing hero, who parlayed his sporting fame into election to the influential Senate last year, also reiterated his willingness to fight mixed martial arts star Conor McGregor if his potential superfight with Floyd Mayweather fails to materialise.
"It could be possible if there is an intention to negotiate (for) the fight but definitely in boxing, not in an MMA fight," he said.
But the 1.69 metre (5ft 6in)-tall Pacquiao also said he was not giving up his position as a playing coach in the Philippines' highly-competitive professional basketball league, despite criticism of his hardcourt performance and Senate duties.
Pacquiao, who plays for the Mahindra Floodbuster team but who has missed practice because of his other roles, said he was not giving up his place on the squad.
"I just make sure that whatever I do outside does not affect my work in Senate," he said.
Pacquiao has previously used his fame to earn a fortune as a TV host and has even made forays into singing and acting.
The Filipino southpaw briefly retired from the ring after beating American Tim Bradley in Las Vegas in April but soon made a comeback, saying he still felt like a youngster.
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 Jessie Vargas in Las Vegas.