WARSAW, Poland — Clearly anxious, President Volodymyr Zelenskyy of Ukraine went in person last week to see NATO defense ministers in Brussels, worried that the war between Israel and Hamas will divert attention — and needed weapons — from Ukraine’s long and bloody struggle against the Russian invasion.

American and NATO officials moved to reassure Zelenskyy, pledging another $2 billion in immediate military aid.

But even before the war in the Mideast began, there was a strong sense in Europe, watching Washington, that the world had reached “peak Ukraine” — that support for Ukraine’s fight against Russia’s invasion would never again be as high as it was a few months ago.

The new run for the White House by former President Donald Trump is shaking confidence that Washington will continue large-scale support for Ukraine. But the concern, Europeans say, is larger than Trump and extends to much of his Republican Party, which has made cutting support for Ukraine a litmus test of conservative credibility.

Even in Europe, Ukraine is an increasingly divisive issue.

Voters in Slovakia handed a victory to Robert Fico, a former prime minister sympathetic to Russia. A vicious election campaign in Poland, one of Ukraine’s staunchest allies, has emphasized strains with Ukraine. A far-right opposed to aiding Ukraine’s war effort has surged in Germany, where Chancellor Olaf Scholz is struggling to win voters over to his call for a stronger military.

“I’m pessimistic,” said Yelyzaveta Yasko, a Ukrainian member of Parliament who is on the foreign affairs committee. “There are many questions now — weapons production, security infrastructure, economic aid, the future of NATO,” she said, but noted that answers to those questions had a timeline of at least five years.

“We have been fighting for 600 days,” she added, “and I don’t see the leadership and planning that is required to take real action — not just statements — in support of Ukraine.”

Even more depressing, Yasko said at a recent security forum in Warsaw, Poland, is the way domestic politics are “instrumentalizing Ukraine.”

The previous bipartisan support for Ukraine in the United States no longer seems to hold.

“There’s less pushback against the anti-Ukrainian stuff already out there,” said Toomas Hendrik Ilves, the former president of Estonia, mentioning the Republican right wing and influential voices like Elon Musk. “It’s dangerous.”

Should Washington cut its aid to Ukraine, top European officials, including the European Union’s head of foreign affairs and security policy, Josep Borrell, acknowledge that Europe cannot fill the gap.

He was in Kyiv, Ukraine’s capital, when Congress excluded support from Ukraine in its temporary budget deal. “That was certainly not expected and certainly not good news,” Borrell told a summit meeting of EU leaders this month in Spain.

“Europe cannot replace the United States,” he said, even as it proposes more aid. “Certainly, we can do more, but the United States is something indispensable for the support to Ukraine.”

That same day, President Vladimir Putin of Russia said that without Western aid, Ukraine could not survive more than a week.

Meanwhile, Ukrainian officials reported intense combat as Russian forces relentlessly assaulted the eastern Ukrainian city of Avdiivka for a fifth consecutive day Saturday. Around 1,600 civilians remain within the city, a stark contrast to its prewar population of about 31,000.