Two dozen countries, led by France and Britain, pledged Thursday to join a “reassurance” force on land, at sea and in the air to patrol any agreement to end the war, unleashed by Russia’s February 2022 invasion.

Tens of thousands have been killed in three-and-a-half years of fighting, which has forced millions from their homes and destroyed much of eastern and southern Ukraine in Europe’s bloodiest conflict since World War II.

Kyiv says security guarantees, backed by Western troops, are crucial to any peace deal, in order to ensure Russia does not re-invade in the future.

“If some troops appear there, especially now during the fighting, we proceed from the premise that they will be legitimate targets,” Putin said at an economic forum in the far eastern city of Vladivostok.

He added that the deployment of such a force was not conducive to long-term peace and said Ukraine’s closer military ties with the West were one of what he calls the “root causes” of the conflict.

Ukraine’s allies have not revealed any specific details of the plan, including how many troops it would involve and how specific countries would contribute.

Zelensky said Friday there was an agreement for “thousands” of troops, but did not give a specific figure.

“It will definitely not be single digits, but in the thousands. And that is a fact, but it is still a little too early to talk about it,” he said during a press conference with European Council President Antonio Costa in western Ukraine.