Tensions are flaring between the Ukraine and Russia as Kiev accuses Moscow of gathering tanks on the border.
Ukrainian President Volodymyr Zelensky said Russia had built-up substantial forces on the border and called it a “provocation”.
Washington has responded, pledging to stand by Ukraine in the event of Russian hostility.
The BBC reports US forces in Europe are on higher alert to “escalations of Russian aggression” in the area.
Weeks of renewed frontline clashes have raised fears of an escalation of the long-simmering conflict in eastern Ukraine, where Kiev’s forces are battling pro-Russian separatists.
Russia and the Ukraine have been in conflict since 2014 when Russian soldiers — without insignia — took control of the Ukrainian territory of Crimea.
Russia then annexed Crimea after a highly-suspicious referendum in which 97 per cent voted for integration into the Russian Federation. The two sides are also involved in conflict in the Donbass region.
Disturbing videos of tanks gathering
Numerous videos have appeared on social media in recent days showing military forces gathering in the region.
There are reports of large-scale Russian military movements to the Ukraine border.
Moscow’s regional partner Belarus has also reportedly deployed troops near the Ukrainian border.
The New York Times reports an estimated 4000 Russian troops have been dispatched the region.
It’s unclear if Russia is planning military action or is sending a message to the Ukrainian leadership.
Russia recently conducted military exercises in the area.
Michael Kofman, a senior research scientist with CNA said it was a sizeable deployment and done in a way intended to be visible.
“This so far does not appear to be the sort of force size one would expect for an invasion of Kherson Oblast or a large-scale operation along those lines,” he said.
“There is a host of other activity along Ukraine’s borders, which consequently raises questions about intentions.”
Russia warns US not to send troops to Ukraine
Speaking to reporters on Friday, Kremlin spokesman Dmitry Peskov said Russia would be forced to respond if the US sent troops to Ukraine.
“There is no doubt such a scenario would lead to a further increase in tensions close to Russia’s borders. Of course, this would call for additional measures from the Russian side to ensure its security,” Mr Peskov told reporters.
He declined to specify which measures would be adopted, while insisting that Russia was not making moves to threaten Ukraine.
“Russia is not threatening anyone, it has never threatened anyone,” Mr Peskov said.
His comments come after the United States warned Russia against “intimidating” Ukraine, with both Defence Secretary Lloyd Austin and Secretary of State Antony Blinken calling their Ukrainian counterparts to stress support.
The Pentagon said earlier this week that US forces in Europe had raised their alert status following the “recent escalations of Russian aggression in eastern Ukraine”.
Rise in violence
Moscow and Kiev this week blamed each other for a rise in violence along the frontline that has undermined a ceasefire brokered last year.
Mr Zelensky said Thursday that 20 Ukrainian servicemen had been killed since the start of the year.
Ukraine’s military intelligence accused Russia of preparing to “expand its military presence” in the separatist-controlled regions.
Moscow has repeatedly denied sending troops and arms to support the separatists and the Kremlin this week said that Russia is at liberty to move troops on its own territory.
“Russia is not a participant of the conflict,” Peskov said Friday, accusing Ukraine’s armed forces of “multiple” provocations in the region.
A senior Russian official dismissed reports of Russia planning an attack on Ukraine as “fake”.
“Russia is not interested in any conflict with Ukraine, especially a military one,” deputy foreign minister Andrei Rudenko told state news agency RIA Novosti.
Biden offers his support
The call was Mr Biden’s first conversation with Mr Zelensky since the US leader’s inauguration in January.
It also came as tensions between the United States and Russia have hit rock bottom after Biden last month infuriated Moscow by agreeing with a description of his Russian counterpart Vladimir Putin as a “killer”.
Mr Zelensky said in a video released by his office that, “President Biden assured me that Ukraine will never be left alone against Russian aggression.”
– with AFP