VietJoy

O'Brien called it "strong evidence and strong intelligence," while adding, "Unfortunately we're not going to be able to get into sorts of methods at this time, but I can tell you it was very strong.”

Pompeo said, "We could see clearly that not only had Soleimani done all the things that we have recounted, like hundreds of thousands of massacres, enormous destruction of countries like Lebanon and Iraq, where they denied...people in those two countries what it is they want, sovereignty, independence and freedom. This is all Soleimani's handiwork. Then we would watch as he was continuing the terror campaign in the region...."

"If you're looking for imminence, you need look no further than the days that led up to the strike that was taken against Soleimani," Pompeo said, including the late December attack that killed an American contractor working in Iraq.

Pompeo added that there were "continuing efforts on behalf of this terrorist to build out a network of campaign activities that were going to lead potentially to the death of many more Americans."

The top U.S. diplomat concluded that the drone attack "was the right decision, we got it right. The Department of Defense did excellent work. The president had an entirely legal, appropriate basis, as well as a decision that fit perfectly within our strategy on how to counter the threat of malign activity from Iran."

Iran has vowed to exact revenge for Soleimani's killing, with O'Brien saying, "We take those seriously and we're watching and monitoring them." But with Trump threatening to respond to any new Iran attack, O'Brien said, "We hope that they're deterred, and that they think twice about attacking America and its interests.”

Even as threats and counter-threats ricocheted between Washington and Tehran, O'Brien said he believes the world is a safer place with the killing of Soleimani.

"Look, over, over the past four months, the two greatest terrorist threats in the world, (Islamic State leader Abu Bakr) al Baghdadi and Soleimani, have both been taken off the battlefield," O'Brien said outside the White House. "I think that makes us safer, and in fact we've been congratulated and told that privately by world leaders from every region in the world who've reached out to congratulate us for this activity.”

In Iran, officials delayed Soleimani's burial, state media reported, after more than 50 people were killed in a stampede of mourners and more than 200 others injured.

Tens of thousands of people had gathered to honor Soleimani in his hometown of Kerman before his planned burial, following similar ceremonies this week in Tehran, Qom and Ahvaz.

Many of the mourners screamed for retaliation against the United States for the killing of Soleimani. "No compromise, no submission, revenge!" they shouted.   

Soleimani's killing has sparked fears of a wider conflict as the United States and Iran threatened strong responses to each other's actions.

Iranian Foreign Minister Mohammad Javad Zarif contended in a CNN interview that the U.S. killing of Soleimani, commander of the Revolutionary Guard's Quds Force, constituted "state terrorism."

“This is an act of aggression against Iran, and it amounts to an armed attack against Iran, and we will respond," Zarif said. "But we will respond proportionately - not disproportionately...we are not lawless like President Trump.”

With heightened tensions between the United States and Iran, Washington has denied Zarif a visa to travel to New York for upcoming United Nations meetings. Pompeo refused to spell out the reasons behind the denial of the visa.

Following the airstrike, Iran announced it was further cutting its compliance with the 2015 agreement that restrained its nuclear program. That prompted Trump, who withdrew from the deal and applied new sanctions against Iran, to tweet Monday, "IRAN WILL NEVER HAVE A NUCLEAR WEAPON!"

   
Trump also vowed late Sunday that the U.S. will strike "very hard and very fast" at as many as 52 Iranian targets if Iran attacks U.S. personnel or assets.  The number 52 represents the number of Americans Tehran took hostage in 1979 for 444 days.

"They're allowed to kill our people," Trump told reporters aboard Air Force One. "They're allowed to torture and maim our people. They're allowed to use roadside bombs and blow up our people and we're not allowed to touch their cultural sites? It doesn't work that way." Pompeo said the U.S., in any new attacks on Iran, would act according to international legal constraints on warfare, under which attacks on cultural sites are considered a war crime.

Iranian President Hassan Rouhani rebuffed Trump's threat on Monday, tweeting, "Those who refer to the number 52 should also remember the number 290. #IR655. Never threaten the Iranian nation."

It was a reference to the U.S. mistakenly shooting down an Iranian passenger jet flying over the Persian Gulf in 1988, killing all 290 people aboard the aircraft. Then-U.S. President Ronald Reagan expressed deep regret over the incident and the U.S. paid nearly $62 million in reparations to the victims' families.