Without divulging details about what led to the early morning airstrike at Baghdad's international airport that killed Soleimani and nine others, the president said the United States "caught" the general "in the act and terminated him.”
“Soleimani made the death of ... people his sick passion,” he added.
The killing of Soleimani, the head of Iran's elite Quds Force, marks a major escalation in the standoff between Washington and Iran, which has careened from one crisis to another since Trump withdrew from the 2015 nuclear deal and imposed crippling sanctions.
Senior State Department officials described the killing as a defensive strike supported by solid intelligence, claiming Soleimani was planning imminent attacks against United States interests and personnel in the region.
The officials said the attacks were being planned in Iraq, Syria and Lebanon, targeting US diplomats, military personnel and facilities that house Americans. They claimed hundreds of Americans could have been killed.
The officials disputed the characterization of an assassination – which are against the law – instead describing it as an action taken in self-defense.
Meanwhile, Iran has vowed "harsh retaliation" for the U.S. airstrike near Baghdad's airport that killed Soleimani.
Iran's Supreme Leader Ayatollah Ali Khamenei warned that "harsh retaliation is waiting" for the U.S. after the airstrike, calling Soleimani the "international face of resistance." Khamenei declared three days of public mourning and appointed Maj. Gen. Esmail Ghaani, Soleimani's deputy, to replace him as head of the Quds Force.
It has also touched off a fresh partisan clash on Capitol Hill — with Republicans cheering the death of the brutal military commander as long overdue, and Democrats voicing concerns that they weren’t consulted and that it could drag the U.S. into a new Middle East conflict.
Sen. Tom Cotton, R-Ark., said Soleimani got what he “richly deserved.”
“Qassem Soleimani masterminded Iran’s reign of terror for decades, including the deaths of hundreds of Americans,” he said. “Tonight, he got what he richly deserved, and all those American soldiers who died by his hand also got what they deserved: justice. America is safer now after Soleimani’s demise.”
Democrats, meanwhile, described the killing as a dangerous escalation, with Sen. Tim Kaine, D-Va., grouping it with the Iran deal pullout as a brazen decision that makes the region less stable.
Kaine called on Congress to act to “stop President Trump from entangling America in yet another unnecessary war in the Middle East.”
The United States said Friday it was sending nearly 3,000 more Army troops to the Middle East and urged American citizens to leave Iraq "immediately." The State Department said the embassy in Baghdad, which was attacked by Iran-backed militiamen and their supporters earlier this week, is closed and all consular services have been suspended.
Fox News' Nick Kalman and Adam Shaw and The Associated Press contributed to this report.