Donald Trump's shifting rhetoric on Iran war works against his rapidly thinning credibility

On Easter Sunday, US President Donald Trump was threatening Iran that it would be "living in hell", accompanied by violent profanities, which shocked United States politicians across the spectrum and led some to describe him as "unhinged".

The next day, Trump threatened Iran again, this time accompanied by the Easter Bunny.

The US president has made well over 30 declarations since early March that the US has "won the war"; "defeated Iran"; is about to win the war; doesn't need the help of other countries and does need other countries' help.

He has also said the US is talking to Iran, while threatening to bomb a country of 90 million back to the Stone Age. 

Trump's increasingly erratic language means that a US president's word — which would have once been regarded with gravitas — holds perhaps only the same weight as the word of the "evil" regime he says he has obliterated several times.

When he got up to speak at a press conference at the White House briefing room on Tuesday morning (Australian time), the sense that time is now working against his rapidly thinning credibility was palpable.

After setting a number of deadlines in recent weeks, then backing away and extending them, Trump doubled down at the press conference, saying that Iran has until 8pm Tuesday US time (10am Wednesday AEST) to meet his conditions or face devastating new air strikes across Iran, from which "it will take them 100 years to rebuild".

Three proposals on a ceasefire

The United States's 15-point plan to end the war has not been publicly outlined, but was first proposed on March 25 and rejected by Iran.

Israel's Channel 12 said components included: a 30-day ceasefire; the dismantling of Iran's nuclear facilities; a permanent commitment from Iran to never develop nuclear weapons; limits on the range and number of Iran's missiles; ending Iran's support for regional proxies; reopening the Strait of Hormuz; and removing all sanctions on Iran.

Al Jazeera reports that Pakistan, which has become the intermediary of choice between the United States and Iran, has proposed a two-stage plan — the Islamabad Accord — involving an immediate 45-day ceasefire that includes the reopening of the Strait of Hormuz.

The proposal is that a final agreement would include Iranian commitments not to pursue nuclear weapons in exchange for sanctions relief and the release of frozen assets.

The news service quoted Iran's spokesman from the ministry of foreign affairs, Esmaeil Baghaei, saying Iran would never accept a 15-point plan put forward by the US.

"Such proposals are both extremely ambitious, unusual and illogical," he was quoted as saying.

According to Iranian state media, Iran has also delivered a 10-point proposal to end the war.

The New York Times reports that it includes a guarantee that Iran would not be attacked again, an end to Israeli strikes against Hezbollah in Lebanon, and the lifting of all sanctions.

In return, Iran would lift its blocking of the Strait of Hormuz and instead impose a fee for passage through the critical waterway, which would be split with Oman, and use its share of the proceeds to reconstruct infrastructure.

Significantly, there is no talk of a ceasefire or of opening the strait during a ceasefire, which others have been proposing.

It is war, or it is a stop to war, on terms that seem impossible to be agreed to by Israel, let alone the United States.

The Strait of Hormuz is a bargaining chip

There seem to be small areas for possible accommodation between the earlier 15-point plan and the later 10-point plan.

For example, Iranian claims for compensation have been morphed into a "toll" paid on the Strait of Hormuz.

But the bottom line remains that Iran is not going to open the Strait of Hormuz until it gets a deal it can live with.

It is its strongest bargaining chip.

And the blocked strait is the biggest domestic and international problem for Trump.

That's because of the devastating impact it is having on the global economy and because it is the most glaring example of how, despite all the US military power, it is Iran calling the shots in this war, not Trump.

Trump could choose to escalate further

In an effort to counter Iran, the US president has issued threats that experts and politicians say could amount to wide-scale international war crimes — from bombing bridges to power plants.

War crimes come up frequently in this conflict because, for starters, the United Nations Charter prohibits unprovoked attacks against other countries.

"All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations," it says.

But Trump has once again escalated the spectre of the United States openly planning to commit war crimes with his declaration that he would wipe out Iranian infrastructure — not just some of it, but all of it.

Under international law, a nation's military is allowed to strike civilian power plants and other key infrastructure only if it contributes to a military operation and civilian harm is minimised.

The Wall Street Journal has previously reported that aides to Trump have said narrowly focused US strikes are allowable because they are meant to hamper Tehran's ability to build missiles, drones and nuclear weapons.

Asked on Monday, local time, if targeting civilian infrastructure would violate international law, the US president responded: "I'm not worried about it."

"You know what's a war crime? Allowing a sick country with demented leadership to have a nuclear weapon," he added.

That is a sentiment most people around the globe would agree with, though it is unlikely to be the basis for any agreement.

Laura Tingle is the ABC's Global Affairs Editor.