Donald Trump on September 24 used his speech before the UN General Assembly to call on nations to act against Tehran and not "subsidise Iran's bloodlust".

The US president has come under pressure to explain how his policy of unilaterally and abruptly withdrawing the US from the multilateral nuclear deal in May 2018—a move that uprooted conventions on international diplomacy given that his predecessor Barack Obama, the Iranians, the UK, Germany, France, Russia and China in November 2015 signed the accord professing good faith—and switching to a policy of hitting the Iranian economy with a backbreaking sanctions regime is supposed to have progressed peace and security in the Middle East. That’s particularly been the case since pre-dawn attacks on oil facilities on September 14 wiped out half of Saudi Arabia’s oil production capacity, with Riyadh and Washington immediately pointing the finger at Tehran for the drone and cruise missile strikes while the Iranians claimed they were the work of Houthis fighting Saudi-backed forces in Yemen’s civil war.

Trump, who in the eyes of some analysts has had his dangerous, unnecessary and foolhardy bluff called by Iran and now looks weak by failing to launch military retribution against the Iranians in response to the attacks on Saudi Arabia, essentially doubled down on his sanctions policy in his address at the UN headquarters in New York.

"One of the greatest security threats facing peace-loving nations today is the repressive regime in Iran," Trump told gathered world leaders.

Denouncing "four decades of failure" since the Islamic revolution in 1979, he called for Iran's leaders to "finally put the Iranian people first," and warned that US sanctions would not be eased unless Tehran changed its behaviour.

"All nations have a duty to act," Trump said. "No responsible government should subsidise Iran's bloodlust. As long as Iran's menacing behaviour continues, sanctions will not be lifted. They will be tightened."

The nuclear deal was drawn up to shield Iran from heavy sanctions in return for verified compliance with measures barring any path Tehran might take to building a nuclear weapon. When Trump yanked the US out of the deal, all the other signatories stayed in, pointing out that UN inspectors were confident in Iran’s compliance.

Trump has demanded a new accord that would mean Iran agreeing to even harsher restrictions aimed at keeping its nuclear programme civilian, plus limits placed on its ballistic missile programme and measures that would bar its provision of support militias in Middle East conflict zones that variously oppose Israel and Arab allies of the US, such as Iran’s regional arch rival Saudi Arabia.

In his speech, Trump also accused Iranian leaders of "fuelling the tragic wars in both Syria and Yemen".

Thousands of people have been killed in the Yemen fighting, widely seen as a "humanitarian nightmare". Both sides have accused each other of human rights violations, while the UK is under fire for providing the Saudis with munitions that have been dropped on Yemeni civilians.

In his speech at the General Assembly, French President Emmanuel Macron urged Iran and the US to pursue negotiations. He said: "Now more than ever is the time for negotiations between Iran, the United States, the signatories of the [nuclear pact], and regional powers, centred on the region's security and stability."

The attack on Saudi Arabia had "changed the situation" in the Gulf region, Macron also said. "Today the risk is of a conflagration arising from a miscalculation or a disproportional response."

However, on the sidelines of the UN General Assembly Trump on September 23 dismissed Macron’s recent attempts to mediate between the US and Iran. “We don’t need a mediator,” said Trump. “He’s [Macron] a friend of mine, but we’re not looking for any mediators. They know who to call.”

Despite, Trump's disinterest in mediators, late on September 24 Pakistan’s Prime Minister Imran Khan said the US president had asked him to help defuse tensions with Iran and that he immediately went to speak with Iranian President Hassan Rouhani. “I can’t say anything right now more than this, except that we are trying and mediating,” Khan told reporters outside the General Assembly.

German Chancellor Angela Merkel met Rouhani on September 24 in New York. She told reporters that she had told him she would welcome talks between Washington and Tehran. She also said that it was unrealistic for Tehran to believe US sanctions would be withdrawn before the talks take place, something which Iran is insistent on.

On September 23, Iranian Foreign Minister Mohammad Javad Zarif ruled out the possibility of negotiating a new nuclear deal with the major powers. There have been moves by the UK and France to start talks aimed at taking things in that direction, but on Twitter Zarif said that the big European powers—namely the UK, France and Germany, collectively referred to as the E3—had failed to fulfil their commitments under the 2015 pact. Iran has been scaling down its compliance with the accord as a reaction to what it sees as Europe’s stark failure to protect its trade and economy from the US “economic war” and “economic terrorism”.

“E3’s paralysis in fulfilling their obligations w/o US permission has been clear since May 2018 ... No new deal before compliance w/ current one,” Zarif wrote on Twitter.

Iran is particularly angry at US moves made since May aimed at driving all of the Islamic Republic’s lifeline crude oil exports off world markets. The economic damage wrought by the Americans’ sanctions regime is causing terrible suffering for ordinary Iranians, it says.

There is no sign of a meeting between Trump and Rouhani taking place in New York.

Trump has also lately seen his diplomatic initiative aimed at bringing enough stability to war-ravaged Afghanistan to enable a big withdrawal of US troops hit the wall. In his address, he blasted the Taliban for choosing to "continue their savage attacks".

"While anyone can make war, only the most courageous choose peace," the US president said. "America's goal is not to go with these endless wars."