WASHINGTON • United States President Donald Trump said on Friday he ordered the killing of a top Iranian general "to stop a war", not start one, but in the tense aftermath, the Pentagon braced itself for retaliation by sending more troops to the Middle East.
Democrats complained that Mr Trump had not consulted Congress, and some worried that the strike made war more likely.
Secretary of State Mike Pompeo argued the US case with allies in the Middle East and beyond, asserting that Friday's drone strike killing Major-General Qassem Soleimani was a necessary act of self-defence.
He asserted that Maj-Gen Soleimani was plotting a series of attacks that endangered many American troops and officials across the Middle East.
In brief remarks to the nation, Mr Trump said the Iranian general had been plotting "imminent and sinister" attacks.
At the Pentagon, Army General Mark Milley, chairman of the Joint Chiefs of Staff, said the US had "compelling, clear, unambiguous intelligence" of Maj-Gen Soleimani plotting violent acts.
"Oh, by the way, it might still happen," Gen Milley said, referring to the planned attacks.
Mr Trump called Maj-Gen Soleimani a ruthless figure who "made the death of innocent people his sick passion... We take comfort in knowing that his reign of terror is over".
The President warned Iran against retaliating. He said the US military has Iranian targets "fully identified" for counter-retaliation. The US has a wide range of offensive and defensive forces in the Gulf area within range of Iran.
As Iran warned of "harsh" reprisals, the US Homeland Security Department watched for trouble brewing on the domestic front and reported "no specific, credible threats" in the first hours after the American attack in Baghdad, said the department's acting secretary, Mr Chad Wolf.
Democrats in Congress questioned the administration's approach, while making clear they do not regret Maj-Gen Soleimani's demise.
Senator Mark Warner noted that Mr Pompeo said the administration wants to "de-escalate" tensions with Iran.
"I think the jury's out on that," he said. "I hope they're successful on that. I think it could have brought in more congressional leaders and allies to help make that case ahead of time."
Representative Adam Schiff, a California Democrat, noted that Congress did not authorise the strike even as he said that Maj-General Soleimani was responsible for "unthinkable violence" and the "world is better off" without him.
"American people don't want a war with Iran. All steps must now be taken to protect our forces against the almost inevitable escalation and increased risk," he tweeted, hours after the strike.