Washington, Apr 9 (IANS): The US is "increasingly concerned" by the Russian military build-up on its border with Ukraine, the White House said, adding that Moscow now has more troops on that frontier since 2014.
"The US is increasingly concerned by recent escalating Russian aggression in eastern Ukraine, including Russian troop movements on Ukraine's border," White House Press Secretary Jen Psaki told reporters during a briefing on Thursday.
"Five Ukrainian soldiers have been killed this week alone. These are all deeply concerning signs," she added.
She also noted that Russia currently deployed more troops along the border than any time since 2014, when the conflict in eastern Ukraine broke out, reports Xinhua news agency.
The ongoing conflict has killed some 14,000 people and left as many as 40,000 wounded.
Kremlin Deputy Chief of Staff Dmitry Kozak said on Thursday that Russia would be forced to defend residents in eastern Ukraine's Donbas, which comprises the Donetsk and Luhansk regions, if there is a need to do so.
Such a decision will depend on the scale of violence in the region, Kozak said, adding that the "armed formations" in Donbas are experienced and currently able to defend themselves without external assistance.
He reiterated that Russia does not want to violate Ukraine's sovereignty or seize its territories.
Last week, President Joe Biden affirmed the US "unwavering support for Ukraine's sovereignty and territorial integrity" to his Ukrainian counterpart Volodymyr Zelensky.
The conflict in eastern Ukraine has been escalating since February and the clashes between the Donbas insurgents and Ukrainian government forces intensified despite the ceasefire secured in July last year.
Insurgents have controlled parts of Donbas along the Russian border for almost seven years.
According to UN estimates, more than 13,000 people have been killed since then.
Despite an agreed ceasefire, at least 21 soldiers have been killed on the government side since the beginning of the year.
According to the separatists, about 23 people have been killed in the same period.