Ukraine's defence minister said on Saturday his country could be provoked by Russian aggravation of the situation in the conflict area of Ukraine's eastern Donbass region.
The minister, Andrii Taran, said Russian accusations about the rights of Russian-speakers being violated could be the reason for the resumption of armed aggression against Ukraine.
"At the same time, it should be noted that the intensification of the armed aggression of the Russian Federation against Ukraine is possible only if an appropriate political decision is made at the highest level in the Kremlin," he said in a statement.
Britain and the United States "firmly opposed" Russia's campaign to destabilize Ukraine and called on Russia to deescalate the situation, UK Foreign Secretary Dominic Raab said on Sunday.
"@SecBlinken (U.S. Secretary of State Antony Blinken) & I agreed Russia must immediately de-escalate the situation & live up to the international commitments that it signed up to at @OSCE (Organization for Security and Co-operation in Europe)," Raab said in a tweet.
Kyiv has raised the alarm over a buildup of Russian forces near the border between Ukraine and Russia, and over a rise in violence along the line of contact separating Ukrainian troops and Russia-backed separatists in Donbass.
The Russian military movements have fuelled concerns that Moscow is preparing to send forces into Ukraine. The Kremlin denies its troops are a threat, but says they will remain as long as it sees fit.
Senior Kremlin official Dmitry Kozak last week said Russia would be forced to defend its citizens in eastern Ukraine depending on the scale of the military conflict there.