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WASHINGTON — President Donald Trump seemed to seek a de-escalation Wednesday in the rising military conflict with Iran, saying Tehran "appears to be standing down" after its missile attack on U.S. targets in Iraq.

In a 10-minute White House speech, Trump vowed to keep up the pressure on Iran with "punishing" new sanctions on top of the heavy economic restraints already in place, but didn't suggest the U.S. would be taking any additional military action in response.

"Iran appears to be standing down, which is a good thing for all parties concerned and a very good thing for the world," Trump said. "No American or Iraqi lives were lost because of the precautions taken, the dispersal of forces and an early warning system that worked very well."

Trump made the comments in an address to the nation Wednesday from the White House less than a day after Iran fired more than a dozen ballistic missiles at two Iraqi air bases housing U.S. and coalition forces in retaliation for the killing of a top general.

Full coverage: Stories and analysis on the Iran crisis

His remarks were seen as an attempt to lower the temperature on the increasing hostilities between the two countries, taking advantage of an off-ramp Iran seemed to be providing by avoiding casualties in the strike and choosing a U.S. military target inside Iraq rather than American civilians.

Iranian Foreign Minister Mohammed Javad Zarif said Wednesday that his country did not "seek escalation or war, but will defend ourselves against any aggression."

Trump continued to make his case against Iran, a message popular with his base of supporters, and defended his killing of Soleimani, calling the Iranian general the "world's top terrorist." He warned that the U.S. was developing "many hypersonic missiles" to counter Iran should it seek to obtain a nuclear weapon and continue its state-sponsored terrorism.

"The civilized world must send a clear and unified message to the Iranian regime: Your campaign of terror, murder, mayhem will not be tolerated any longer," Trump said. "It will not be allowed to go forward."

While the president appears to have the support of Republicans for his recent actions against Iran, he has repeatedly pledged to end the wars in Iraq and Afghanistan and promised to withdraw U.S. troops from both nations, a key campaign promise in 2016.

Flanked by several top officials including Vice President Mike Pence, Secretary of State Mike Pompeo and Defense Secretary Mark Esper, Trump also announced "additional punishing economic sanctions" on the Iranian regime that will "remain until Iran changes its behavior."

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He also said he planned to request help from NATO, an alliance he has frequently criticized.

"I am going to ask NATO to become much more involved in the Middle East process," he said without elaborating.

Trump again criticized the Iran nuclear deal — from which he withdrew the U.S. in 2018 — and claimed that the financial incentives provided by the Obama administration to Iran under that deal financed the missiles used in the latest attacks.

"The missiles fired last night at us and our allies were paid for by the funds made available by the last administration," Trump said, adding that "Iran's hostilities increased" after the deal was signed in 2015.

Trump, however, mischaracterized the deal that then-President Barack Obama brokered with Iran, claiming that the U.S. had given Iran billions.

Trump said Iran, under the deal, was "given $150 billion, not to mention $1.8 billion in cash," according to the White House transcript of his remarks.

The U.S. freed up billions of Iran's own money that had been frozen for decades — they did not pay off the regime. And $150 billion is a high-end estimate of the dollars freed by the deal, according to fact-checkers. The U.S. Treasury in 2015 estimated that it was around $50 billion.

Trump also overestimated the amount of cash the U.S. gave to Iran to reconcile a contract dispute between the two countries over weapons Iran had paid for but America had not delivered decades ago. It was $1.7 billion, not $1.8 billion.

Trump also called on world powers, including the United Kingdom, Germany, France, Russian and China, to "break away from the remnants of" the deal. The White House said Trump had spoken with British Prime Minister Boris Johnson and "agreed to continue close coordination in support of shared national security interests."

Washington and Tehran both confirmed that Iran was the source of the missiles launched overnight.

One target was the Ain al-Asad air base, which is around 100 miles northwest of Baghdad and was visited by Trump in 2018. The Pentagon did not directly name the second base but said it was in or around Irbil, Iraq's second-largest city in the Kurdish-run north of the country.

The attacks at 1:20 a.m. local time (5:30 p.m. ET on Tuesday) came after Iranian leaders had promised "revenge" and "harsh retaliation" for the death last week of Gen. Qassem Soleimani, who was killed in a U.S. drone strike in Iraq.

The U.S. blamed Soleimani, a high-profile commander of Iran's secretive Quds Force, for a spate of rocket attacks in recent months, including one that killed a U.S. contractor in late December.

Republicans praised Trump for his remarks Wednesday, emphasizing that he had not announced any military retaliation against Iran for their attack.

"Retaliation for retaliation's sake is not necessary. There were no Americans killed," Sen. Lindsey Graham, R-S.C., told NBC News.

Rep. Mark Meadows, R-N.C., another close Trump ally, tweeted that Trump had made "it clear that America's strongly preferred option is de-escalation — not war."

Some observers speculated that Iran had intentionally designed their attack against the U.S. to be relatively modest with the intent of providing Trump a so-called off-ramp from further confrontation.

House Democrats huddled behind closed doors Wednesday morning and were briefed on the situation by former Obama administration officials Wendy Sherman, who as an ambassador played a lead role in crafting the Iran deal, and Avril Haines, former assistant to the president and deputy national security adviser.

Emerging from the meeting, Democrats stressed that Congress must assert its authority over declaring war even if the U.S. and Iran de-escalate tensions.

"It's very important that Congress, in a very strong way, reassert its authority in ensuring that we do not go to war without an authorization from Congress," said Rep. David Cicilline, D-R.I., a member of Democratic leadership.

Rep. Adriano Espaillat, D-N.Y., said that Congress's ability to wage war is in the Constitution and that "we should never dilute our congressional authority."