Russia and NATO members exchanged barbs on Wednesday, with nerves on edge as each side warned the other to stay within its borders.
The war of words comes as more than 10,000 Russian troops engaged in manoeuvres in the country's south-west, near the Ukrainian border, according to the Defence Ministry in Moscow.
In 2014, Russian troops massed along the border, presaging the start of a pro-Russian rebellion in eastern Ukraine that has never ended, as well as Russia's annexation of the Crimea.
Just days ago, Ukrainian President Volodymyr Zelensky warned that Russia is poised to attempt a coup in Ukraine.
US Secretary of State Antony Blinken emerged later on Wednesday from a meeting with other NATO representatives to warn that the build-up of Russian troops at the border was part of a plot against Ukraine.
"We’re deeply concerned by evidence that Russia has made plans for significant aggressive moves against Ukraine. The plans include efforts to destabilize Ukraine from within, as well as large scale military operations," Blinken said, threatening Moscow with "severe costs" if it went ahead.
"NATO is prepared to reinforce its defences on the eastern flank," Blinken added.
He urged both sides to return to peace talks known as the Minsk Protocol. "Diplomacy is the only responsible way to resolve this potential crisis."
His comments came the same day Ukrainian Foreign Minister Dmytro Kuleba asked NATO allies to to help stave off a potential Russian incursion with strong political signals, the preparation of economic sanctions and more military backing.
"If we act in a coordinated fashion, we will be able to deter President Putin and to demotivate him from choosing the worst case scenario, which is a military operation," Kuleba said at NATO talks in Riga.
On Monday, Kuleba alleged that there were now 115,000 Russian troops stationed near the border. These figures could not be independently verified.
Moscow, for its part, accused NATO of encroaching upon Russia.
Putin demands 'guarantees'
President Vladimir Putin demanded "guarantees" that NATO would not strengthen its presence near Russian borders.
"We will be insisting on concrete agreements, which exclude any possible NATO expansion to the east, and the deployment of any weapons that threaten us and are deployed in the approximate vicinity of the Russian territory," Putin said during a meeting at the Kremlin with foreign diplomats.
He also expressed concern that NATO infrastructure had stretched quite close to Russian territory, and that Ukrainian forces have massed their armies near territory controlled by pro-Russian militias in the country's east.
In his annual state-of-the-nation address in parliament on Wednesday, Zelensky spoke out in favour of direct negotiations with Russia to resolve the ongoing conflict in eastern Ukraine.
"We must acknowledge the truth that we cannot end the war without direct negotiations with Russia," he said.
According to UN estimates, about 13,000 people have died in Ukraine since the conflict began seven years ago.
Kiev is not part of NATO, but is a close ally and is supposed to eventually join the 30-member military pact. NATO supports the Ukrainian armed forces with training and equipment.
Fresh sanctions
NATO states, including the United States, also indicated this week they would be prepared to resort to fresh economic sanctions if Moscow were to send troops over the border. Western countries already slapped punitive measures on Russia over the Ukraine conflict.
"Allies are making sure that Ukraine has the means to defend itself, and at the same time, the alliance will look at what it needs to do in the event of further Russian aggression to shore up its own defences," said Blinken.
NATO foreign ministers agreed that Moscow would be made to pay a high price for any aggression on Ukraine, NATO Secretary General Jens Stoltenberg said.
While increased military assistance was possible, a direct military intervention by NATO in case of an invasion was not on the cards, he said. Ukraine is not part of NATO so allies are not treaty-bound to defend the state.
It also remains to be seen whether Russia would indeed risk such an escalation.
And, in another provocation to Ukraine, Belarusian President Alexander Lukashenko - a close ally of Moscow - recognized the annexed Ukrainian Black Sea peninsula of Crimea as Russian for the first time after a long period of hesitation.
"Crimea is ... de facto a Russian Crimea," Lukashenko said in an interview with the Russian state agency Ria Novosti, excerpts of which were published on Wednesday.
