Doing so would require the Russian leader to “accept the failure of sitting down with a president he considers a joke from a country that doesn’t exist”

Geneva, Istanbul and Budapest have been put forward as potential locations - but bilateral talks still remain a long way off.

Ukrainian President Volodymyr Zelensky said Russia was doing everything it could to stop a meeting between him and Vladimir Putin from taking place, while Russia's foreign minister said the agenda for such a summit was not ready.