World leaders gathered on Tuesday in New York City for the 74th session of the UNGA.
The meeting came against a backdrop of tension in the Middle East over recent attacks on Saudi Arabian oil facilities, which the US blames on Iran, allegations that Tehran denies.
Millions of young climate change activists across the world in the same week took to the streets demanding greater action from those in power.
French President Emmanuel Macron said world leaders lacked courage but needed it to build peace and take responsibility.
Macron said it was "time to restart negotiations between the United States, Iran, the signators of the JCPOA and the powers of the area concerning first of all the security and stability of the region."
He said negotiations needed to include preventing Iran from getting a nuclear weapon, ending the crisis in Yemen, finding a security plan for the region, and ending economic sanctions.
"I am not naive, and I don't believe in miracles," he said. "I believe in the courage to build peace. I know that the United States of America, that Iran, that all of the signatories of the accord have this courage," Macron said.
German Chancellor Angela Merkel spoke on the sidelines of the General Assembly about relations between the US and Iran, stating that she would welcome stalks between the states but didn't think it was realistic that sanctions would be lifted first.
Donald Trump declared that the "future belongs to patriots", not globalists, as he addressed the United Nations General Assembly (UNGA).
The US president said wise leaders put their own people and countries first: "The free world must embrace its national foundations - it must not attempt to erase them or replace them."
Trump also used his speech to attack China and Iran, the former over its "unfair" trade practices, and the latter for being what he called the biggest state sponsor of terrorism in the world.
He held out hope that the US and China could reach a deal to end their trade dispute.
Trump went over a litany of what he called China's unfair trade policies. "It has embraced an economic model dependent on massive market barriers, heavy state subsidies, currency manipulation...forced technology transfers and the theft of intellectual property, and also trade secrets on a grand scale," he said.
"As far as America is concerned, those days are over."
He wasn't the first world leader to attack another nation in his speech, even though he was only the second to speak.
Brazilian president Jair Bolsonaro opened the speeches of world leaders, calling on other South American nations to help restore democracy to Venezuela, which he criticised for its socialist government.
The far-right politician also dismissing reports that the Brazilian Amazon rainforest is being destroyed by fire, as claimed by "lying" media.
He accused foreign nations of being interested in the region's mineral wealth and biodiversity, instead of its indigenous people.
Turkish President Recep Tayyip Erdogan talked about the separation between nuclear powers and non-nuclear states, stating that the inequality was "enough to undermine global balances."
"The possession of nuclear power should either be forbidden for all or permissible for everyone," Erdogan said.
British Prime Minister Boris Johnson on Tuesday joked that if some British members of parliament had their way Brexit would be an endless process like the torment of the Greek mythological figure Prometheus.
According to the online Encyclopedia Britannica, the Greek god Zeus punished Prometheus for stealing fire from the gods by securing him to a mountain and sending an eagle to eat his liver, which regrows only to be eaten again and again.
"This went on forever, a bit like the experience of Brexit in the UK, if some of our parliamentarians had their way," Johnson told the annual gathering of world leaders for the United Nations General Assembly in a late Tuesday speech
The general debate is taking place from September 24-September 30, with several world leaders set to address the General Assembly.
This year's theme is: "Galvanizing multilateral efforts for poverty eradication, quality education, climate action and inclusion."
Watch live coverage in the player above as world leaders deliver their addresses.