Mr Trump said Soleimani “was planning a big attack” when he was killed in a US drone strike in Baghdad last Friday.
But Mr Trump appeared to draw back from a threat to target Iran’s cultural sites should Tehran respond militarily.
Iran was burying Soleimani on Tuesday, but a stampede at the funeral killed 50 people and injured 200 more.
In remarks at the Oval Office, President Trump also addressed the issue of Iraq, saying a US withdrawal of troops would be the worst thing for the country.
His comments came in the wake of a letter, which the US military said had been sent in error, to Iraq’s prime minister, apparently agreeing to a request by Iraqi MPs to pull troops out.
Soleimani’s killing has raised fears of a conflict between the US and Iran.