John Bacon and Tom Vanden Brook | USA TODAY

USA TODAY

The U.S. military had advance warning of Iran's missile assault on two Iraqi bases housing U.S. forces, attacks that prompted a vow of new economic sanctions Wednesday from President Donald Trump.

Trump, addressing the nation, said no deaths or injuries resulted from the attacks. He said Iran appeared to be "standing down" and announced no military reprisal for the missile attack, but said "powerful sanctions'' would be imposed until Iran changed its ways.

"Iran must abandon its nuclear ambitions and end its support for terrorism," he said.

Iran fired more than a dozen missiles Tuesday in retaliation of a U.S. drone strike days earlier that killed one of Tehran's most powerful military leaders, Qasem Soleimani. The missiles targeted al Assad air base in Iraq’s western Anbar province and another base in Erbil in Iraq’s semi-autonomous Kurdish region.

The extent of damage to the bases was not immediately clear, but early-warning defense systems gave U.S. forces advance knowledge that missiles had been launched, according to a U.S. official speaking to USA TODAY on the condition of anonymity.

Assassination or legitimate act? Legal debate rages as Iran retaliates

The official, who was not authorized to speak publicly, added that a hangar was damaged at al Assad, a sprawling complex 100 miles west of Baghdad that houses about 1,500 coalition forces.

But the warnings allowed troops and other personnel to scramble into hardened bunkers for safety. U.S. and coalition personnel in Iraq on the mission to combat ISIS have been practicing drills for missile attacks for some time, the official said.

“The early-warning system worked,” the official said.

Gen. Mark Milley, chairman of the Joint Chiefs of Staff, also credited the system for preventing casualties, telling reporters the missiles were sent with the intent of doing serious harm, not merely to create the illusion Iran was retaliating.

“I believe based on what I saw and what I know that they were intended to cause structural damage, destroy vehicles and equipment and aircraft and to kill personnel,” Milley said.

Majid Takht Ravanchi, Iran's U.N. Ambassador, said in a letter to that body that his country simply exercised its right to self-defense by taking proportionate measures and “does not seek escalation or war.”

Iraqi Prime Minister Adil Abdul Mahdi said in a statement Wednesday that Iran notified Iraq the attack “had begun or would begin shortly,” on unspecified U.S. military locations. The U.S. military reported the attack at the same time, he said.

CNN, citing an Arab diplomatic source, reported that Iran notified Iraq in advance and that Iraqi officials then tipped U.S. troops before the attack began. A U.S. defense official also told CNN that Iraqis were told by Iran to stay away from certain bases.

The militaries of Finland and Lithuania, which had personnel at one of the targeted bases, said they also received information about an imminent attack and had time to take shelter or leave the base.

AP

Iranian state TV aired video of what commentators described as the missiles being launched. Iran Foreign Minister Javad Zarif later said his country had "concluded proportionate measures" in response to a "cowardly armed attack against our citizens."

Fahim Masoud, Middle East intelligence manager for the risk assessment firm WorldAware, warned that Zarif's statement does not mean Iran will stop using its proxies and cyberwarfare capabilities to attack U.S. troops, interests and assets.

"Soleimani's killing was the most consequential event in the Middle East since the invasion of Iraq," he told USA TODAY in an email. "Its consequences will reverberate through the region for several years."

Still, conventional war with Iran is not likely due to its outdated weaponry and an economy that is on the verge of collapse, he said.

"The Iranian regime wants to survive," he said.

'This was an act of war': Lawmakers react to Iran's missile strike on US military bases

Trump said he would not let Iran become a nuclear power, blasting the previous nuclear deal with Iran from which the U.S. controversially withdrew. He said a better deal has to be arranged and the civilized world must send a message that "your campaign of terrorism will not be tolerated anymore."

James Piazza, a Penn State professor specializing in Middle East issues, told USA TODAY that Trump failed to provide "any reassuring information" on how he would keep Iran from developing nuclear capability. Nor did Trump indicate how he might build international support for more Iran sanctions, Piazza said.

"The president has so thoroughly alienated traditional U.S. allies, I am not very optimistic that he will be able to put more pressure on Iran with allied help and support," Piazza said.

Iran Supreme Leader Ayatollah Ali Khamenei reiterated his nation's position that the U.S. must exit Iraq – and the Middle East.

"They were slapped last night, but such military actions are not enough," he said. "This region won’t accept the US presence."

Meanwhile, NATO has temporarily suspended training of counter-ISIS forces in Iraq, a NATO official who was not authorized to speak publicly told USA TODAY. Some of the military personnel have been moved to new positions in and outside of Iraq, the official said.

NATO Secretary General Jens Stoltenberg condemned the missile attack.

"NATO calls on Iran to refrain from further violence," he said. "Allies continue to consult and remain committed to our training mission in Iraq."

Contributing: The Associated Press

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Life inside the Ain Assad air base in Iraq