British Foreign Secretary Liz Truss on Thursday repeated to Russia that any incursion into Ukraine would be a costly move, as diplomatic tension in the region simmered.
Russian troops have been massing along the border with Ukraine over the past few months, and Ms Truss warned that any intrusion would be a “massive strategic mistake”.
“I condemn the Kremlin’s aggressive and inflammatory rhetoric against Ukraine and Nato," she said.
“Nato is a defensive alliance and Ukraine continues to show commendable restraint in the face of Russian provocation and aggression.
“Russia’s military build-ups on the border of Ukraine and in illegally annexed Crimea are unacceptable.
“Any Russian incursion would ... be met with strength, including co-ordinated sanctions with our allies to impose a severe cost on Russia’s interests and economy.
“The UK’s support for Ukraine is unwavering.”
But Ms Truss also welcomed Moscow's willingness to enter talks due to take place in January. She said Russia must "de-escalate its activities" and engage in serious discussions.
The Kremlin denies it plans to invade and says the West is gripped by Russophobia.
Moscow says the expansion of Nato threatens Russia and has contravened assurances given after the Soviet Union collapsed in 1991.