Boris Johnson says there is "no way Ukraine is going to join Nato anytime soon" but stresses the decision has to be for the country's president to take.
On Tuesday Ukrainian President Volodymyr Zelensky said it was important to recognise that Ukraine would not be a member of Nato, saying: "We have heard for many years about the open doors, but we also heard that we can't enter those doors."
Speaking during his visit to Abu Dhabi, the UK prime minister says he has talked with Zelensky again and says he understands what he is saying about Nato.
He adds the most important thing is that Russian President Vladimir Putin's "absolutely barbaric attacks on Ukraine should stop" and must not be seen to have succeeded.