US Defense Secretary Mark Esper on Wednesday said the US strike that killed a top Iranian general had restored credibility to the US threat to Tehran to restrain itself militarily."I believe that we've restored a level of deterrence with them," he said.But Washington security analysts say it is far from certain that Tehran has been deterred from further attacks on the United States and its allies, and that it might not be long before it challenges President Donald Trump again.In the short run tensions could ease after Iran retaliated for Revolutionary Guards Commander Qasem Soleimani's death last week by firing 12 ballistic missiles at two US bases in Iraq, causing damage but killing no one.But that is "just the beginning," said Kaleigh Thomas, a Middle East security analyst at the Center for a New American Security.Soleimani's death in a US drone strike last Friday "has definitely changed the tone of tensions going forward," she said."They're going to be planning strategically, investing in ways to inflict pain on the United States."Tehran tentativeFor effective deterrence, Thomas said, the Trump administration lacks a coherent message that Tehran can make sense of - what response it can expect from the United States to what provocative actions - as well as a back channel to communicate, like previous administrations had.She faulted Trump's inconsistent responses last year after the Revolutionary Guards shot down two US drones, allegedly damaged multiple tankers in the Gulf, and allegedly launched missiles on Saudi oil installations.ALSO READ | 'We don't retreat in face of America': Iran presidentIn each case the US response was hesitant and minimal, emboldening Tehran."A lot of deterrence ... is this idea of, there are patterns, and that way, everyone's kind of on the same page," said Thomas. "If we're reading two different books, something's gonna go wrong."Tehran might now be tentative about reacting, but is "motivated to act and to find ways to inflict pain upon the United States."Proxy forcesRetired General David Petraeus, who once led US forces in the Middle East, said he was optimistic that killing Soleimani delivered a strong message that Tehran will have to heed.It was "a very significant effort to re-establish deterrence, which obviously had not been shored up by the relatively insignificant responses up until now," Petraeus told Foreign Policy magazine.MUST READ | 'Slap in the face' - Iran supreme leader on missiles fired at US troop bases in IraqFormer US senior diplomat Nicolas Burns said it was "far too early" to declare success in delivering a credible threat message to Tehran."Iran has a brutal history of using proxy forces to attack the US and others," he told AFP. "They could well do that in the coming weeks or months."Iran's nuclear threatMore challenging is Tehran's threat this week to restart its program to develop nuclear weapons by producing weapons-grade uranium.OPINION | Soleimani does not deserve our tearsThomas said the US inability to deter Iran is rooted in Trump's unilateral decision in 2018 to pull out of the Iran nuclear deal which froze that program, and place more sanctions on the country.After that, she said, "I think it was it was total confusion about what United States actually wanted from Iran.