The leaders of Germany, France and Ukraine have called on Russia to pull its troops back from the Ukrainian border.
Ukraine’s president Volodymr Zelensky proposed a summit that would also include Moscow – which Kyiv fears is preparing an invasion.
The conflict dates back to 2014, when Ukraine’s pro-Russian president was ousted in a popular uprising. Moscow-backed separatists occupied the eastern Donbas region – and Russia annexed Crimea.
The Kremlin says its recent military buildup is a response to Nato threats and Ukrainian provocations.
More than 14,000 people have died in fighting in eastern Ukraine. Violations of a shaky truce have become increasingly frequent in recent weeks.