"It was a fully authorized action under the 2002 AUMF [Authorization for Use of Military Force]," O'Brien said on Friday.

The United States, O’Brien added, also calls on Iran to return to the negotiating table and warned Iranian leadership against retaliation. O'Brien urged Iran to halt its nuclear program and end its proxy wars.

Soleimani had traveled to Iraq from Damascus where he was plotting attacks against US personnel, O'Brien said. Trump decided that there was a greater risk to not conduct the attack than to do it, he added.

O'Brien said he could not give further details about Soleimani's plans to attack US personnel due to the sensitive timing of the situation.

O'Brien said the administration will give members of Congress classified briefings about the strike when they return to Capitol Hill next week.

Tensions are high across the Middle East after the United States killed Soleimani in an airstrike on the outskirts of Baghdad. The US Embassy in Baghdad on Friday called on US citizens to depart Iraq as soon as possible.

Iran’s National Security Council said in a statement it will respond to Soleimani's death "at the right time and in the right place."