Ukrainian president Volodymyr Zelensky has criticised the “absurd” absence of a timetable for his country to join Nato as leaders met at a summit in Lithuania.

President Joe Biden described the Nato gathering as a “historic moment” and said the US agreed with a proposal, yet to be released publicly, to outline a path for Ukraine’s eventual membership.

However, Mr Zelensky, who was on his way to Vilnius to join the summit, expressed disappointment at how the negotiations were playing out.

“We value our allies,” he wrote on Twitter but added that “Ukraine also deserves respect”.

“It’s unprecedented and absurd when timeframe is not set neither for the invitation nor for Ukraine’s membership,” Mr Zelensky said. He added: “Uncertainty is weakness. And I will openly discuss this at the summit.”

A public flash of anger from the Ukrainian leader, who has been hailed by the West as a hero for his leadership during the Russian invasion, could renew tensions in Vilnius just as they had begun to subside.

On Monday evening, the night before the summit opened, Turkey withdrew its objections to Sweden joining the alliance, a step toward the unity that Western leaders have been eager to demonstrate in the face of Russia’s invasion of Ukraine.

Lithuania NATO Summit
Joe Biden has welcomed the prospect of Sweden joining Nato (Mindaugas Kulbis/AP)

The deal was reached after days of intensive meetings, and it is poised to expand the alliance’s strength in northern Europe.

“Rumours of the death of Nato’s unity are greatly exaggerated,” Jake Sullivan, the US national security adviser, told reporters triumphantly on Tuesday.

According to a joint statement issued when the deal was announced, Mr Erdogan will ask Turkey’s parliament to approve Sweden joining Nato. Hungarian prime minister Viktor Orban is expected to take a similar step.

The outcome is a victory for Mr Biden as well, as he has described Nato’s expansion as an example of how Russia’s invasion of Ukraine has backfired on Moscow.

Finland has already become the 31st member of the alliance, and Sweden will become the 32nd. Both Nordic countries were historically non-aligned until the war increased fears of Russian aggression.

Because of the deal on Sweden’s membership, “this summit is already historic before it has started,” Nato secretary-general Jens Stoltenberg said.

Lithuania NATO Summit
Sweden would become the 32nd member of Nato (Kevin Lamarque/AP)

Kremlin spokesman Dmitry Peskov told reporters that Nato’s expansion is “one of the reasons that led to the current situation”.

“It looks like the Europeans don’t understand their mistake,” Mr Peskov said. He warned against putting Ukraine on a fast track for Nato membership.

“Potentially it’s very dangerous for the European security, it carries very big risks,” Mr Peskov said.

Mr Biden began Tuesday by meeting Lithuanian president Gitanas Nauseda, where he emphasised his commitment to transatlantic cooperation.

“Nothing happens here that doesn’t affect us,” he told Mr Nauseda. The White House said Mr Nauseda presented Mr Biden with the Order of Vytautas the Great, the highest award a Lithuanian president can bestow. Mr Biden is the first US president to receive it.

Mr Biden and Mr Erdogan were scheduled to meet on Tuesday evening, and it was unclear how some of the Turkish president’s other demands will be resolved.

He has been seeking advanced American fighter jets and a path toward membership of the European Union. The White House has expressed support for both, but publicly insisted that the issues were not related to Sweden’s membership of Nato.

“I stand ready to work with President Erdogan and Turkey on enhancing defence and deterrence in the Euro-Atlantic area,” Mr Biden said in a statement on Monday.