United States President Donald Trump was due to meet his Ukrainian counterpart Volodymyr Zelensky on Tuesday before attending a United Nations summit in New York.
It will be his second meeting with Zelensky since Trump met with the Russian President Vladimir Putin on 15 August.
The talks broke Moscow's isolation in the West but yielded no breakthrough on Ukraine.
Russia has not only kept up its attacks on Ukraine in the past month, but has raised fears in the West with drone or air incursions in NATO members Poland, Estonia and Romania.
Mike Waltz, the US ambassador to the UN, voiced solidarity over the airspace violations.
"The United States and our allies will defend every inch of NATO territory," said Waltz.
During his campaign to become president for a second time, Trump boasted that he could end the Ukraine war within one day and vaunted his personal chemistry with Putin.
But during a state visit to the United Kingdom, Trump said Putin had not engaged with proposals to end the conflict.
“I thought this war would be one of the easiest to solve because of my relationship with Putin," said Trump who was flanked by the British Prime Minister Keir Starmer during a press conference.
"But he has really let me down. I mean, frankly, Russian soldiers are being killed at a higher rate than the Ukrainian soldiers. But, yeah, he’s let me down.”
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Zelensky is expected to press Trump to take a harder line and impose new sanctions on Russia.
But US Secretary of State Marco Rubio last week said that Trump was not ready to pressure Putin, adding that without him "there's no one left in the world that could possibly mediate" on Ukraine.
Zelensky is expected to tread carefully with Trump who, along with Vice President JD Vance, berated him openly during a meeting in February at the White House and called him ungrateful for billions of dollars in US military assistance.
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Attacking 'globalist' institutions
Trump, a native New Yorker, is spending barely a day in town for the week-long summit.
One of his few other one-on-one meetings will be with Argentina's President Javier Milei, an ideological ally to whose government the US is considering offering an economic lifeline.
White House Press Secretary Karoline Leavitt said that Trump would discuss the renewal of American strength around the world.
"The president will also touch upon how globalist institutions have significantly decayed the world order, and he will articulate his straightforward and constructive vision for the world," she told reporters in Washington.
Trump in his second term has moved more aggressively in his "America First" vision of curbing cooperation with the rest of the world.
He has moved to pull the US out of the World Health Organization and the UN climate body, severely curtailed US development assistance and wielded sanctions against foreign judges over rulings he sees as violating sovereignty.
"Instead of inflaming global crises and fueling chaos and inequality, he should use his power and influence to work with the global community to provide meaningful solutions," said Abby Maxman, president and CEO of Oxfam America.
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'Use of influence'
Trump's appearance will take place a day after French President Emmanuel Macron led a group of Western allies of the United States in recognising a Palestinian state, a historic but largely symbolic step opposed by Israel.
"The time for peace has come, as we are just moments away from no longer being able to seize it," Macron said in his address to the UN General Assembly.
"The time has come to free the 48 hostages held by Hamas. The time has come to stop the war, the bombings of Gaza, the massacres and the displacement."
Macron, however, said France would not open an embassy for a Palestinian state until a ceasefire is in place in Gaza and all the remaining hostages taken on 7 October 2023 have been released.
The Palestinian Authority hailed France's "historic and courageous" decision and its delegation gave him a standing ovation.
Representatives for the US and Israel were absent during Marcon's speech.
