Live updates: follow the latest news on Russia-Ukraine
British Prime Minister Boris Johnson said on Wednesday there was “currently little evidence of Russia disengaging” from its military build-up near Ukraine, in a phone call with UN Secretary General Antonio Guterres.
“The leaders reiterated states' responsibility to abide by their obligations under the United Nations Charter and to respect the sovereignty and territorial integrity of UN members,” Mr Johnson's office said in a readout of the call.
The pair also agreed that any Russian invasion of Ukraine would have “catastrophic and far-reaching consequences”, a Downing Street spokeswoman added.
The call came on the eve of a UN Security Council meeting on Thursday to discuss the crisis on Ukraine's borders, where Moscow has amassed more than 100,000 soldiers.
Britain will be represented at the meeting by Europe Minister James Cleverly, Downing Street noted.
Mr Johnson and Mr Guterres “reaffirmed the importance of all parties working in good faith” to enact existing agreements struck by Ukraine, Russia and mediating countries concerning the region's security, it added.
“They agreed to continue working closely together to pursue an urgent diplomatic resolution and avert a disastrous military escalation and humanitarian crisis,” the Downing Street spokeswoman said.
Late on Wednesday, Britain's head of military intelligence said that Russia is continuing to move forces towards the border with Ukraine despite claims by Moscow that it is pulling back.
Chief of Defence Intelligence Lt Gen Sir Jim Hockenhull said there had been sightings of additional armoured vehicles, helicopters and a field hospital near the border.
“We have not seen evidence that Russia has withdrawn forces from Ukraine’s borders,” he said.
“Contrary to their claims, Russia continues to build up military capabilities near Ukraine.”
He added that Russia currently has the military mass in place to conduct an invasion.
