US officials are reportedly concerned that describing the path to joining the alliance as “irreversible” would be unacceptable to some members, including Hungary.

However, some other members say that Ukraine has yet to meet the criteria for entry by reforming its government.

Joe Biden, the US president, said earlier this month that he opposed the “Nato-isation” of Ukraine as part of a peace deal with Russia, pointing to “corruption” in Kyiv.

Antony Blinken, his secretary of state, said that Nato would provide “concrete steps to bring Ukraine closer” this year, and create a “bridge to membership…that is strong and well-lit”.

Escalation with Russia

Some believe that setting a deadline for Ukraine to join the alliance risks dragging the whole bloc into a war with Russia if peace is not achieved by that date.

Under the terms of the North Atlantic Treaty, an attack on one member state is considered an attack on them all.

If Ukraine joined the alliance while at war with Russia, all other signatories to the treaty would be obliged to come to its aid.

Mr Zelensky has repeatedly requested a firm timeline for Ukraine to join the bloc, arguing that its membership would deter Russia on the country’s Eastern flank, where the war continues.

At last year’s summit, he described the vague membership offer when “conditions are met” as “unprecedented and absurd”.

The Ukrainian president’s outburst was described as a “disaster” by a senior Nato official, who warned that the alliance had to avoid a repeat scenario in Washington.

“We need to have a consensus before the Washington summit,” they added.