Russia was warned against an escalation of fighting in eastern Ukraine by Kiev’s government as the hostile rhetoric between the neighbouring countries showed no sign of abating.
Ukrainian Foreign Minister Dmytro Kuleba, alongside counterparts from Baltic former Soviet states, accused officials and commentators in Moscow of verbal intimidation.
He also called for stronger Western backing and said “words of support aren't enough”.
Tensions were again soaring in eastern Ukraine as the recent build-up of Russian forces on the border and on the annexed Crimean peninsula was condemned by Kiev and Nato powers.
"They are openly threatening Ukraine with war and the destruction of Ukrainian statehood," Mr Kuleba said on Thursday, during the visit of senior diplomats from Estonia, Latvia and Lithuania.
"The red line of Ukraine is the state border. If Russia crosses the red line, then it will have to suffer.”
Lithuanian Foreign Minister Gabrielius Landsbergis said Ukraine would never be left on its own.
“We stand with you, we stand in solidarity," he said.
Moscow and Kiev blame each other for the surge in violence, which Ukraine said led to the death of at least 28 Ukrainian soldiers.
Russia said the massing of troops was to conduct military drills in response to threatening Nato actions. The Kremlin accused western countries of arming Ukraine.
"We are not afraid. Ukraine itself is strong enough and has reliable friends to defend its statehood," Mr Kuleba said.
"It is important to make Russia clearly understand that the consequences in the event of military adventures on its part will be very painful."
The US introduced sanctions against Russia for cyber attacks it allegedly carried out, including during the 2020 US presidential elections.
Nato backed the move by its member state and said allies were “taking actions individually and collectively to enhance the alliance’s collective security”.
It called on Russia “to cease its provocations and to immediately de-escalate tensions on Ukraine’s borders and in illegally annexed Crimea”.
But Nato left the door open to dialogue with Moscow, should certain conditions be met.
“While we continue to ensure our deterrence and defence posture, Nato remains open to periodic, focused and meaningful dialogue, and to a constructive relationship with Russia when Russia’s actions make that possible,” Nato said.