An international relations expert warns Iran has "completely called Trump's bluff" - and the situation could develop into "full-blown war".
University of Waikato international law expert Prof Alexander Gillespie told Newshub the chances of a peaceful resolution are "diminishing by the minute" as tensions between Iran and the US grow.
The death of Iranian General Qassem Soleimani in a United States-directed airstrike on Friday led to revenge attacks on Wednesday on two United States airbases in Iraq. US President Donald Trump had previously said the US would target 52 Iranian sites if Iran retaliated.
"Iran is not blinking, they're confronting America, they're confronting Trump whether he wants it or not," Gillespie told Newshub.
"I think Trump has made a mistake and he assumed they're scared of him - but they feel the provocation is so great."
Gillespie says the US might have expected Iran to follow its previous responses during periods of conflict. These include using proxy forces to launch attacks on US allies and shutting down international shipping in the Strait of Hormuz. But instead, Iran has escalated to a direct - though limited - military attack.
"The first thing to note is Iran is not adopting an indirect strategy of using proxies," he says.
"Things to look for is the strike, it's a contained strike. They have not unleashed hundreds of missiles. They're trying to make a proportionate response.
Gillespie says Trump now has three options in response to the attacks.
"Option one, he doesn't do anything and he finds a diplomatic way of resolving this," he says.
"Option two, he keeps it proportionate and fires missiles at two Iranian bases. And option three he fires missiles at all 52 sites."
Gillespie warns that if the US does hit 52 targets this will lead to "full-blown war" and he's concerned Trump will choose some kind of military action.
"It's whether Trump takes this on the nose or if he decides to unleash hell upon them," he says.
"He can either back away and take the slap and try to put pressure on Iran in other ways - things don't include shooting - but I don't think he will do that.
"I think he's backed himself into a corner."