Former British Prime Minister Boris Johnson told CNN there was “no possible justification” to delay Ukraine’s NATO membership while urging the United States not to tire of supporting Ukraine against Russia, saying victory over Moscow it is imperative.

In an interview with CNN after the conclusion of the NATO summit on Wednesday, Johnson called on the US to continue its support for Ukraine, including a steady supply of arms.

Referring to the question of Ukraine joining NATO, he said that “there can be no possible excuse or reason for us to continue to laugh and delay”, and added that it is “very important” to establish that Ukraine is on the path to joining the NATO. “The last remaining objection was that this would be provocative to Vladimir Putin. Well, we’ve seen what happens when you don’t have Ukraine in NATO, you cause the worst war in Europe in 80 years.”

During his prime ministership, Johnson was a staunch supporter of Ukraine and developed a close working relationship with Zelensky, becoming one of the first foreign leaders to make the perilous trip to Kiev. Johnson resigned as prime minister in September 2022 and as an MP in June in the wake of scandals over his handling of the UK’s coronavirus crisis.

On Wednesday he warned that apart from the Russian military, the biggest enemy Ukrainians have in the conflict is “Ukraine fatigue”. “It is the exhaustion of the rest of the world, and especially the supporters of Ukraine, to ensure that they win.” “But they have to win, it’s absolutely critical,” he added, explaining that Ukraine’s victory is “vital for democracy and freedom around the world.”

In the interview, Johnson also said he supports Biden’s decision to provide Ukraine with cluster munitions, despite the UK’s opposition. “I think President Biden did the right thing, and the sooner the Ukrainians can use them to retake their territory, the more lives will be saved.”