United Nations (United States) (AFP) - Joe Biden gave a somber farewell address to the United Nations on Tuesday, using his own decision to drop out of the US presidential election to warn of the dangers of autocrats around the globe refusing to quit.

“My fellow leaders, let us never forget – some things are more important than staying in power,” Biden said to applause in his final speech at the UN General Assembly in New York.

The 81-year-old exhorted world leaders to stand up for democracy in the face of spiraling turmoil and conflict, urging support for Ukraine and pushing for peace in the Middle East.

With six weeks until a vote that could bring the isolationist and election-denying Donald Trump back to the White House, Biden closed his remarks by drawing lessons from his own life.

He said that over the summer he faced a “difficult decision” about whether to seek a second term. “Being president has been the honor of my life, there’s so much more I want to get done,” Biden said.

“As much as I love the job, I love my country more. I decided after 50 years of public service it’s time for a new generation of leadership to take my nation forward.”

Biden then added to the assembled leaders: “It’s your people that matter the most.”

- ‘Sweep of history’ -

Biden quit the White House race in July after a disastrous TV debate against Trump fueled concerns about his mental acuity, and he has endorsed his vice president, Kamala Harris, as the Democratic nominee.

Allies and adversaries alike are now closely watching the knife-edge November 5 US election to see if Trump and his “America First” foreign policy return.

Biden’s speech marked an attempt to burnish his own legacy after his one-term presidency, while effectively urging other world leaders to protect it from a possible Trump comeback.

Biden said he’d seen a “remarkable sweep of history” during five decades of public service and, as the world reels from a series of crises, “things can get better, we should never forget that.”

He repeatedly pushed the importance of US alliances, many of which the Republican has repeatedly thrown into question.

Reflecting on the chaotic US withdrawal from Afghanistan in 2021 to end his country’s two decades of involvement, Biden said he thought of the US troops killed by a bomb during the pull-out “every single day.”

- ‘Putin’s war has failed’ -

Yet for all the lofty themes, Biden’s speech offered few details on how to solve the foreign policy issues that either Trump or Harris will have to deal with.

He warned against a “full-scale war” in Lebanon without saying how to avoid it, after Israeli strikes targeting Hezbollah that killed at least 558 people on Monday

Biden’s prized goal of a ceasefire in the Gaza war between Israel and Hamas meanwhile looks further off than ever.

On Ukraine Biden was firmer, saying that “Putin’s war has failed” in Ukraine and warned that Kyiv’s allies “cannot grow weary” in their support.

He is due to host Ukrainian President Volodymyr Zelensky – who was in the hall at the UN to watch Biden’s speech – at the White House for talks on Thursday.

Trump in contrast said at a rally on Tuesday that America was “stuck in that war” and that as president he would “get out.”

After his speech, Biden met a host of world leaders including UN Secretary-General Antonio Guterres and Italian premier Giorgia Meloni, with whom he hosted an anti-drugs event.

Biden then rounded off the day with a fresh swipe at Trump in a speech on US climate policy, saying the Republican had “moved the world backwards” while in office.

“And by the way, windmills do not cause cancer,” Biden added with a smile, mocking the Republican’s opposition to wind power.