UK Prime Minister Boris Johnson has warned allies to prepare for a protracted war in Ukraine, urging them to either support Kyiv or jeopardize the “greatest victory for aggression in Europe since the Second World War.”

In an article for The Sunday Times, Johnson noted that Ukraine's foreign supporters “must respond by ensuring that Ukraine has the strategic endurance to survive and eventually prevail.”

To note, on Friday—a day after the visit of the leaders of France, Germany, Italy and Romania to Kyiv—Boris Johnson paid a visit to Ukraine to support the country's aspiration to join the EU.

“Time is the vital factor. Everything will depend on whether Ukraine can strengthen its ability to defend its soil faster than Russia can renew its capacity to attack. Our task is to enlist time on Ukraine’s side,” the UK premier wrote, in particular, in his article.