A dramatic escalation between the United States and Iran appears to have eased, with both rivals seeming to pull back from the verge of a full-blown conflict, even as tensions remain high and experts warn that the confrontation is far from over.

In a White House address on Wednesday, Trump said Iran "appears to be standing down" after it fired more than a dozen missiles at two Iraqi bases housing US troops in retaliation for the US assassination of top Iranian military commander Qassem Soleimani.

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Trump said there had been no US casualties and damage was "minimal" after the attacks, striking a noticeably different tone than his tweets following the killing of Soleimani in which he threatened to "fully strike back" if Iran struck US citizens or assets in the region.

Rather than announce military action, Trump said the US "will immediately impose additional punishing economic sanctions" while it evaluated "options in response to Iranian aggression".

During his own televised address earlier on Wednesday, Iran's Supreme Leader Ali Hosseini Khameini called his country's missile attack a "slap in the face" for the US but said military retaliation was not sufficient.

"What is important is that the corrupt presence of the US in this region should come to an end," he told a large crowd, many of whom were holding pictures of Soleimani, the head of Iran's Quds Force, the overseas arm of the elite Islamic Revolutionary Guard Corps (IRGC).

On Thursday, Soleimani's successor Brigadier General Esmail Qaani said he would continue the "luminous" path pursued by his predecessor, while Tasnim news agency quoted IRGC senior commander Abdollah Araghi as saying that Iran would take "harsher revenge soon".

'Calibrated response'

US officials have said Soleimani, who was charged with extending Iran's military influence beyond its borders, was killed because of intelligence indicating forces under his command planned attacks on US targets in the region. But they have not provided this intelligence.

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Having pledged "severe revenge" for Soleimani's killing, Iran struck the Ain al-Assad airbase in western Iraq and another facility in Erbil in the early hours of Wednesday.

There were no casualties.

"Iran's military retaliation against a military base housing US troops is a very calibrated response; Iran wants to make sure that this a retaliation, not escalation," Ali Akbar Dareini, a researcher at the Center for Strategic Studies, an Iranian government-affiliated think tank, told Al Jazeera from Tehran.

"It appears that Iran is not going to take any further conventional military retaliation against the US," he said, adding, however, that for Iran "a befitting response would be when all the US troops are kicked out of this region".

Al Jazeera's Dorsa Jabbari, reporting from Tehran, said that "the position here is that Soleimani’s assassination is the price the US will have to pay for leaving this region".

"The Iranians want the US troops to leave the entire Middle East, this is something, they say, is not negotiable - until that happens, this back-and-forth rhetoric between the two sides will continue and the tensions will keep increasing."

Douglas Ollivant, director for Iraq at the US National Security Council under President George W. Bush and Barack Obama, said the missile attack appeared to be meant "as a message".

"No one was killed, and I think we've found no serious damage to any material - in that sense this was de-escalatory," he told Al Jazeera.

Ollivant argued that while the targeting of Ain al-Asad was expected, the firing at Erbil was "intended to be a powerful psychological message for the region".

"That if you have a base that is hosting US troops and if attacks are launched from there, you just made yourself a legitimate target."

While Iran might have limited its response to a brazen but carefully calibrated strike on US bases in Iraq, this is probably not the end of the story. From this point on and depending on US reaction, indirect retaliation might become the name of the game. — Ali Vaez (@AliVaez) January 8, 2020

'Full-blown confrontation'

Making good on an election promise, Trump in May 2018 unilaterally withdrew Washington from the Iran nuclear deal with world powers, formally known as the JCPOA.

The JCPOA had tightly restricted Iran's nuclear programme in return for ending sanctions that had severely damaged its economy.

Following its withdrawal, the US began a "maximum pressure" campaign against Iran, including a series of strangling sanctions.

In response, Tehran reduced its JCPOA compliance, exceeding limitations set by the landmark accord.

As differences over the nuclear deal remain and neither side appears to give in, analysts are still wary of a military escalation.

"You always have to be concerned about full-blown military confrontation when you have lots of people with weapons pointed at each other," Ollivant said.

"The opportunities for miscalculation either at the very senior level or the very low level, then grows and no one can stop. That's always a great possibility."

Ali Vaez, director of the Iran project at International Crisis Group, said: "While Iran might have limited its response to a brazen but carefully calibrated strike on US bases in Iraq, this is probably not the end of the story."

"From this point on and depending on US reaction, indirect retaliation might become the name of the game," he wrote on Twitter.

The strike that killed Soleimani as he drove away in a convoy from Baghdad international airport on Friday also killed Abu Mahdi al-Muhandis, the deputy chief of Hashd al-Shaabi (Popular Mobilisation Forces or PMF), an umbrella organisation of mostly Iran-backed Shia armed groups.

"The US act of war against Iranian and Iraqi military officials in Baghdad did include the killing of several Iraqi officials - the PMF is part of the Iraqi army," Dareini said.

"Iranian allies and groups close to Iran have their own decisions to make and it's very likely that they will take revenge for this killing."

Paramilitary chief Qais al-Khazali on Wednesday said Iraqi forces should respond to the killing of al-Muhandis.



"That response will be no less than the size of the Iranian response. That is a promise," Khazali threatened.

Hours later, two rockets slammed into the Baghdad's Green Zone, the high-security enclave where the US embassy, other foreign missions and some foreign troops are based in the Iraqi capital.