Poland’s head of state has called on Nato powers to give postwar security guarantees to Ukraine, on the eve of a visit by the US president to Warsaw to reaffirm the west’s support for Kyiv a year into Russia’s war.

Andrzej Duda told the Financial Times that promises of security guarantees “would be important” for Ukraine and the morale of its soldiers by underscoring “this feeling that Nato stands with them”.

The call from the Polish president comes as he prepares to host Joe Biden in what is expected to be the key point of the US president’s visit this week to mark the anniversary of Russia’s invasion.

While Ukraine was aware it cannot join Nato now, Kyiv was expecting a “partnership” with “some kind of security guarantees”, Duda said in an interview on the sidelines of the Munich Security Conference.

Duda also urged Biden to reaffirm “in very strong terms” during his Warsaw visit that the US stands unreservedly behind Nato’s Article 5, the collective defence clause treating any attack on a member state as an attack against all.

The security guarantees Ukraine has sought would be structured differently, effectively binding leading Nato powers such as the US, UK and France into providing military assistance in the event of a future attack on Ukraine.

Former Nato secretary-general Anders Fogh Rasmussen, who co-authored a formal proposal for Ukraine’s postwar security with president Volodymyr Zelenskyy’s chief of staff Andriy Yermak, has described such guarantees as similar to what Israel enjoys from the US.

In Munich, US and German officials played down the need for security guarantees at this stage, arguing that the military support being provided to Ukraine is the assurance Kyiv needs.

But Ukraine is adamant that it requires more binding guarantees of military backing after its experience with the 1994 Budapest Memorandum. Under that deal, Ukraine gave up its nuclear weapons in exchange for promises from Russia, the UK and the US not to use military force against it.

Kyiv applied for Nato membership in September, even though allies acknowledge this is not a short-term prospect as long as the war wages on.

Duda’s call for guarantees would require raising Washington’s pledges to Ukraine beyond what Biden has talked about recently. Some other Nato nations also remain wary of binding promises for fear of being dragged into a war with Russia, and instead argue for the strengthening of Ukraine’s military to ensure it can defend itself.

“There is a pretty robust debate going on about security guarantees, but I really don’t think President Biden will want to put this forward now,” said Michał Baranowski, director of the Warsaw office of the German Marshall Fund think-tank. Instead, he said, the US administration is pushing ahead with “a porcupine strategy”, which means “arm Ukrainians to the teeth so that they can deal with Russia directly”.

Biden is visiting Warsaw for the second time in a year and Duda forecast that this week’s trip would have “a huge impact” on “the entire eastern flank of Nato”.

“There’s also a signal sent to US investors,” Duda said, referring to Poland and other countries neighbouring Ukraine. “This place is safe so you can safely invest your money here.”

After ending a lengthy dispute over whether Germany would agree to send German-made Leopard tanks to Ukraine, tensions have now emerged over when the tanks will actually be delivered. Germany last week chided Poland and other countries armed with Leopards for not sending them to Kyiv more quickly.

But Duda said Poland was sticking to its military commitments to Ukraine and that any delay also reflected the need to guarantee the availability of spare parts for the Leopards.

“I don’t quite understand the point made [by Germany]”, Duda said. “It is Germany who is the only producer of spare parts . . . There are no other countries who would be authorised to do that. So unless Germany supplies those spare parts, we have a problem with them.” 

Biden’s stay in Warsaw on Tuesday and Wednesday will include a meeting with the so-called Bucharest Nine group of countries from central and eastern Europe that joined Nato after the collapse of the Soviet Union.

He is scheduled to deliver a speech on Tuesday evening to “make it clear that the United States will continue to stand with Ukraine . . . for as long as it takes”, said John Kirby, a spokesperson for the US National Security Council, who did not rule out a meeting with Zelenskyy during the trip. “We remain in constant communication with the Ukrainians about what their needs are.”

Additional reporting by Lauren Fedor in Washington