White House officials said Biden would make a robust case to members of the world body to continue to back Ukraine's effort to repel a nearly 19-month old Russian invasion that has no end in sight.

Biden previewed his thinking in a pair of fundraisers on Monday evening, telling supporters that he stood up to Vladimir Putin's invasion, and questioning whether Trump, the 2024 GOP presidential frontrunner, would have even attempted to help Ukraine stop the Russian land grab if he were in power.

“I will not side with dictators like Putin. Maybe Trump and his MAGA friends can bow down but I won't,” Biden told supporters at a Broadway fundraiser.

There will be notable absences as the president makes his case before the General Assembly: British Prime Rishi Sunak, French President Emmanuel Macron, Chinese President Xi Jinping and Putin are all skipping the gathering.

For Biden, the more important audience for Tuesday's speech could be closer to home as he looks to make the case to voters that he's skilfully handled a complicated foreign policy agenda and that the experience that comes with age has proved to be an asset. It's an argument that the 80-year-old president is likely to continue to make to try to counter scepticism — even in his own Democratic Party — among voters who are concerned about his age.

“We rallied the world to support Ukraine and united NATO because I was convinced from the beginning that Putin's counting on NATO not being able to stick together,” Biden said at another Monday fundraiser. “He's still trying. And our allies know once again, the United States can be counted on.”

Biden's message of unwavering support for Ukraine will play out as Congress is increasingly divided over providing additional funding for Kyiv.Biden has sought a package of USD 13.1 billion in additional military aid for Ukraine and USD 8.5 billion for humanitarian support. But conservative Republican lawmakers have been pushing for broad federal spending cuts and some of those allied with Trump are specifically looking to stop money to Ukraine.

In addition to underscoring continued US support for Ukraine, Biden is expected to touch on mobilising global resources to combat climate change and bolstering multilateral organisations to help poor and middle-income countries, according to senior administration officials.

Biden aims to send a message that Russia's invasion of Ukraine is in violation of the UN charter and to emphasise that every country has a stake in defending a nation's sovereignty, especially when it is under attack, said the officials, who previewed Biden's activities in New York this week on condition of anonymity.

After his speech, Biden will meet with António Guterres, the UN secretary-general, as well as leaders from the so-called C5 group of Central Asian nations, which include Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan.

The meeting is expected to focus on regional security, trade, climate change, ongoing reforms to improve governance and other issues.

Xi has stepped up his own courting of those countries. During his own summit in May with the Central Asian leaders, Xi promised to build more railway and other trade links with the region and proposed jointly developing oil and gas sources.

White House national security adviser Jake Sullivan told reporters last week that Biden's meeting with those leaders should not be seen as an effort to counterbalance Chinese influence in the region.

“Look, this summit is not against any country,” Sullivan said in previewing the meeting. “It is for a positive agenda that we want to work through with these countries.”

The officials played down the fact that the leaders of the other permanent members of the UN Security Council -– the UK, France, Russia and China — won't be in New York this week and instead emphasised the importance that Biden attaches to showing up at the annual diplomatic forum.

However, Biden does not plan to attend a special summit on climate that Guterres will host on Wednesday, where countries are encouraged to bring new ideas and proposals on how to further cut emissions and combat climate change.?

Officials played down Biden's absence at the climate summit, saying the issue will be interspersed through the president's remarks and events throughout the week. John Kerry, the US climate envoy, is to attend in Biden's place.

Biden plans to meet with Brazilian President Luiz Inácio Lula da Silva on Wednesday, as well as Israeli Prime Minister Benjamin Netanyahu. Senior administration officials said the two leaders will discuss issues including Iran but declined to elaborate further.

Biden is scheduled to host talks Thursday at the White House with Ukraine President Volodymyr Zelenskyy.