US President Donald Trump has said his decision to order the killing of top Iranian general Qassem Soleimani has saved a lot of lives, calling Gen Soleimani “a monster”.

Mr Trump and his top advisers are under pressure to disclose more detail about the intelligence that led to the killing, which has greatly heightened tension with Tehran.

Mr Trump said Tuesday that his decision saved American lives and that members of Congress will be briefed on the reasons for the US attack.

He's been called a monster, and he was a monster, and he's no longer a monster, he's dead

Donald Trump

“We saved a lot of lives,” he said. “They were planning something.”

So far, Mr Trump and top national security officials have justified the air strike with general statements about the threat posted by Gen Soleimani, who commanded proxy forces outside Iran and was responsible for the deaths of American troops in Iraq.

But the details have been scarce.

Mr Trump said:  “He’s been called a monster, and he was a monster, and he’s no longer a monster, he’s dead.

“And that’s a good thing for a lot of countries. He was planning a very big attack, and a very bad attack for us and other people, and we stopped him and I don’t think anybody can complain about it.”

Gen Soleimani was targeted while he was at an airport in Baghdad with Abu Mahdi al-Muhandis, a veteran Iraqi militant who also was killed.

Mr Trump said they were not in Baghdad to discuss holiday plans or visit a “’nice resort”, but were there to talk over “’bad business”.

The lack of detail does not sit well with Democrats, who recall how President George W. Bush justified his invasion of Iraq by accusing Saddam Hussein of having non-existent weapons of mass destruction.

Lawmakers in recent days have been pressing for more detail to explain why Mr Trump ordered the killing – a decision that previous administrations passed up because of fears it would unleash even more violence.

Gen Soleimani travelled frequently and relatively openly, with visits to Baghdad more frequent in recent months. He also often showed up in Syria, including along the border between Iraq and Syria.

Secretary of state Mike Pompeo said it was clear that Gen Soleimani was continuing his efforts to build a network of activities “that were going to lead potentially to the death of many more Americans”.

Defence secretary Mark Esper told reporters that Iranian threats against Americans were “’days away” from being executed.

Democratic lawmakers are not convinced.

Senate Minority Leader Chuck Schumer and Senator Bob Menendez, the top Democrat on the Senate foreign relations committee, called on Mr Trump to declassify the written notification the president sent to Congress after the fatal strike on Gen Soleimani.

The notification was required under the War Powers Resolution Act of 1973, which requires the president to report to Congress when American forces are sent into hostile or imminently hostile situations.

“It is critical that national security matters of such import be shared with the American people in a timely manner,” the senators wrote.

“An entirely classified notification is simply not appropriate in a democratic society, and there appears to be no legitimate justification for classifying this notification.”