President Donald Trump has told the United Nations General Assembly (UNGA) he faces a "big decision" on whether to strike Iran again or pursue a peace deal.
A single member of Iran's delegation watched on during the president's speech on Tuesday in New York, in which he said he could "annihilate" the Islamic Republic if the conflict went unresolved.
Before a standing-room-only audience, Trump also rejected "global government", vowed to broker peace between Russia and Ukraine and ensure the US wins the artificial intelligence race.
His comments came on a day of high-level diplomacy, which included talks between US and Iranian representatives.
Trump himself has been meeting more than a dozen world leaders as wars in the Middle East and Ukraine test his foreign policy agenda.
He began his UNGA speech by touting his accomplishments on the economy, immigration, the border and tackling violent crime, in remarks that sounded more pitched to voters in November's US midterm elections than the diplomats in Manhattan.
He spent much of his address justifying the war with Iran, which has spiked global oil prices while dragging down his approval ratings since the US and Israel launched the military action in February.
Trump's tone contrasted with remarks earlier by UN Secretary General António Guterres, who warned global divisions were deepening and underscored the "interdependence" of the world's peoples.
The US president argued that the conflict had prevented Tehran from obtaining a nuclear weapon and demonstrated the value of what he described as peace through strength - ultimatums rather than deal-making or compromise.
"Will a deal be made with Iran that lets them rebuild and create a far greater country than it ever was before?"
"Or do I annihilate the Islamic Republic and do it quickly, never giving them a chance to kill and destroy people and countries again? Do I drive them into hell?"
Trump said he believed an Iran deal, which has so far eluded him, would come right after November's elections.
The remarks were indicative of his foreign-policy strategy of coercive diplomacy - threatening overwhelming force while keeping negotiations open.
Trump later told reporters that American officials had had a "very productive" three-hour meeting with the Iranian delegation on the sidelines of the general assembly.
Iran state TV confirmed that Foreign Minister Abbas Araghchi had met US Special Envoy to the Middle East Steve Witkoff, although there was no comment from officials in Tehran.
The BBC asked Witkoff how the meetings had gone as he was leaving the UN building and he responded with a thumbs up.
He later confirmed that the talks had been held "through the mediators, who shuttled between the two sides throughout the day."
"They successfully completed a round of discussions that we hope will prove constructive and promising," Witkoff posted on X. "The mediators will continue their work."
In his speech, Trump once again predicted his diplomacy would end Russia's war in Ukraine, which has shown little sign of letting up as the two sides trade tit-for-tat missile and drone strikes deep into each other's territory.
"We're working very closely with the leaders of Russia and Ukraine, and we will get that one done," he said. "It's going to happen, I think, more quickly than people understand."
Trump also played down fears about AI, vowing that the US would not surrender its lead to China because of alarmism or what he described as a "globalist scheme" to control the technology.
The US president argued artificial intelligence should instead be known as "super intelligence".
"The use of the word artificial makes it sound fake," he said. "It's not fake, it's actually amazing. But we have to be careful."
On the sidelines of the general assembly on Tuesday, Trump signed an agreement with the leaders of Denmark and Greenland to beef up US military presence on the North Atlantic island.
The deal reaffirms the sovereignty of Greenland, an autonomous territory of Denmark, but grants the US broad access to the island's airspace and territory.
Trump has also been meeting Ukrainian President Volodymyr Zelensky, British Prime Minister Andy Burnham and leaders from Saudi Arabia, the United Arab Emirates, Qatar, Kuwait, Bahrain and Oman.
This latter meeting, which also involved leaders from other Arab and Islamic countries, "discussed current regional developments and the situation in the Middle East, as well as ways to consolidate security and stability," the UAE's foreign minister said in a statement.
Earlier, Guterres gave his farewell speech as UN secretary general, urging unnamed superpowers to recognise "that their power isn't so super".
"The fault lines in our world are widening," Guterres said, citing geopolitical rivalries, wars, climate change and artificial intelligence.
By contrast, Trump criticised international institutions, accusing the UN of a "far-left agenda of globalist bureaucrats who nobody ever elected".
The US president instead emphasised national sovereignty and "unmatched" American military power.
"There is no global government," he said.
He also warned that the US would not allow threats to establish themselves anywhere in the Western hemisphere.
"If necessary, we will use our unmatched military might to secure the vital national interests of the United States," he said.
Trump accused Cuba's communist government of cultivating ties to left-wing groups in the US, including the Communist Party USA, Antifa and the Democratic Socialists of America.
The Cuban delegation also appeared to walk out of the assembly chamber as Trump turned his sights on them, referring to the island as a "failed state".
