Biden, at UN General Assembly, urges world leaders to stand by Ukraine

US President Joe Biden has appealed to world leaders at the UN General Assembly to stand with Ukraine against Russian aggression.

"Russia believes that the world will grow weary and allow it to brutalise Ukraine without consequence," Biden said in his speech to UNGA on Tuesday.

"If we allow Ukraine to be carved up, is the independence of any nation secure?"

Biden's address at the annual gathering was the centrepiece event of his three-day visit to New York, which will include meetings with the heads of five Central Asian nations and the leaders of Israel and Brazil.

Biden has faced criticism from some Republicans who want the United States to spend less money on the war effort.

Former president Donald Trump, the front-runner for the Republican nomination in the 2024 presidential election, has vowed to seek a quick end to the war if returned to power.

Trump has voiced skepticism about Washington's engagement with traditional allies, including NATO, and has been complimentary of Putin.

House of Representatives Speaker Kevin McCarthy, the leading Republican in Washington, has questioned whether the United States should keep sending billions of dollars in weaponry to Ukraine.

'Nexus of horror'

In his speech, Biden argued that Russia's February 2022 incursion into Ukraine and occupation of territory violated the founding UN Charter, a main principle of which is respect for sovereignty and territorial integrity.

Biden echoed remarks of UN Secretary-General Antonio Guterres who in his opening speech to UNGA on Tuesday said Russia's military offensive "has unleashed a nexus of horror."

A Biden administration official said Biden and US officials would also focus at the UN meetings on mobilising resources for infrastructure and sustainable development and fighting climate crisis.

Solid majorities of Americans support providing weaponry to Ukraine to defend itself against Russia and believe that such aid demonstrates to China and other US rivals a will to protect US interests and allies, according to a Reuters/Ipsos survey in June.

Ukrainian President Volodymyr Zelenskyy, due to speak at UNGA on Tuesday, was expected to visit Biden at the White House on Thursday and to meet some congressional leaders as well.

The United States is preparing a new military aid package for Ukraine to coincide with Zelenskyy's visit, and Congress has been asked to approve billions of dollars more in security assistance for the rest of the year.

"We have confidence that there will be bipartisan support for this. I think President Zelenskyy does as well," White House national security adviser Jake Sullivan told reporters.

After his speech, Biden was due to sit down with UN Secretary-General Antonio Guterres to discuss world hot spots.

Later, he will attend a summit with the presidents of five Central Asian nations, a first. They are Kazakhstan, the Kyrgyz Republic, Tajikistan, Turkmenistan and Uzbekistan.

On Wednesday, Biden will meet Brazilian President Luiz Inacio Lula da Silva and join him in an event with labour leaders from Brazil and the United States.

Also on Wednesday, Biden will have his first face-to-face meeting with Israeli Prime Minister Benjamin Netanyahu since Netanyahu regained power last December.

Sullivan said they would discuss "a vision for a more stable and prosperous and integrated region, as well as to compare notes on effectively countering and deterring Iran."