President Joe Biden urged NATO allies to keep backing Ukraine in its war against Russia as he made a farewell visit to Germany Friday just weeks before US elections.
As Ukraine faces a third winter at war and battlefield losses in the east, Kyiv and its allies fear a potential return of Donald Trump to the White House would mean reduced US military support.
Biden said that Western allies must "sustain our support ... until Ukraine wins a just and sustainable peace".
"We're headed into a very difficult winter. We cannot let up."
Biden then met Chancellor Olaf Scholz, before they were to hold four-way talks with French President Emmanuel Macron and British Prime Minister Keir Starmer.
On Thursday, President Volodymyr Zelensky presented his "victory plan" to the European Union and NATO, but his allies have not agreed to his request for immediate NATO membership.
Washington and London have also rejected Ukrainian requests to be able to use donated long-range weapons for attacks on targets inside Russia, and Berlin has refused to send its own long-range Taurus missile system.
Scholz said: "We are supporting Ukraine as powerfully as we can and at the same time we are making sure that NATO does not become a party to the war, so that this war does not turn into an even bigger catastrophe."
The United States has been by far the biggest supplier of military aid to Ukraine since Russia launched its full-scale invasion in 2022, followed by Germany.
Biden earlier received a red-carpet welcome from President Frank-Walter Steinmeier, who awarded him Germany's highest honour for championing bilateral and transatlantic ties.
The German head of state honoured 81-year-old Biden as "a beacon of democracy" who had shown unwavering support for NATO and Ukraine "in our most dangerous moment since the Cold War".
The other issue in focus was the Middle East conflict, where Biden voiced hope for new momentum toward a Gaza ceasefire after Israel killed Hamas leader Yahya Sinwar.
Biden said the death of Sinwar, considered the architect of the 7 October 2023 attack on Israel, was a "moment of justice".
The US president said he had urged Israeli Prime Minister Benjamin Netanyahu to "also make this moment an opportunity to seek a path to peace, a better future in Gaza without Hamas".
Scholz said that after Sinwar's death, "hopefully the concrete prospect will now open up for a ceasefire and an agreement to release the hostages in Gaza" .
Biden's visit comes as the campaign race heats up ahead of the November 5 election and as allies are nervously eyeing a potential Trump victory over Kamala Harris.
Trump, who during his last term berated NATO allies, has opposed the level of US military support for Ukraine and would be expected to soften US criticism of Israel in its wars in Gaza and Lebanon.
Steinmeier said that just a few years ago in the US-Germany relationship "the distance had grown so wide that we almost lost each other".
"When you were elected president, you restored Europe's hope in the transatlantic alliance literally overnight," Steinmeier said, before awarding him the Grand Cross special class of the Order of Merit.
When Russia invaded Ukraine, Steinmeier said, Russia President Vladimir Putin "thought we would be weak. He thought we would be divided".
"But the opposite was true: NATO was stronger and more united than ever -– and that is in no small part thanks to your leadership," added the German president, exceptionally delivering his speech in English
Biden was originally due in Germany last week for a four-day state visit that would have included a major Ukraine defense meeting with Zelensky.
After cancelling that trip to coordinate the response to Hurricane Milton, Biden was at pains to make his valedictory Germany trip nonetheless, with a stripped-down programme squeezed into a one-day visit.
Among the guests Biden met in Berlin was 102-year old Holocaust survivor Margot Friedlaender, who grew up in Berlin, was interned in the Theresienstadt concentration camp, emigrated to the US and returned to her hometown in 2010.
"I'm actually honoured to be in your presence," an emotional Biden told her at the start of his speech.