The iconic sportsman - who died in 2016 at the age of 74 - was convicted of refusing to turn up for military duty in 1967 after being drafted to fight in the Vietnam War.
Ali was convicted of draft evasion and lost his heavyweight champion title in 1967. However, the Supreme Court ruled in his favor in 1971, ending his legal battle.
Trump told reporters that he was thinking "very seriously" about pardoning him. Ali's lawyer confirmed in a statement that the boxing legend has no use for a pardon. That law made it illegal to transport women across state lines for "immoral" purposes.
Melania Trump First Official Look Following Surgery
The First Lady traveled with President Trump for a follow-up briefing at FEMA headquarters on the ongoing hurricane response. For the past several weeks, rumors have swirled around the first lady's whereabouts after she underwent a kidney operation.
"We appreciate President Trump's sentiment, but a pardon is unnecessary".
He did not offer any other names, but said in response to a reporter's question that O.J. Simpson wasn't on the list.
Earlier this week, he also commuted the life sentence of a woman whose cause was championed by Kim Kardashian West. Last week, the president said he was considering pardoning Martha Stewart and commuting the sentence of former Illinois Gov. Rod Blagojevich. Johnson spent 21 years in prison on those charges.
Mr Trump's comments follow his pardon of conservative political commentator and author Dinesh D'Souza.