Liz Truss has said it would be a “strategic mistake” for Russia to ramp up aggression against Ukraine.
The Foreign Secretary said she was meeting her Ukrainian counterpart on Wednesday to offer “closer strategic co-operation” when she was asked at an event whether the UK could deploy more troops to the country, where it was feared Vladimir Putin may launch an invasion.
She said Russia must “respect the sovereignty and the territorial integrity of Ukraine”.
It comes after it was reported there was little progress in talks between US president Joe Biden and Russian President Mr Putin.
Mr Biden “told President Putin directly that if Russia further invades Ukraine, the United States and our European allies would respond with strong economic measures”, US national security adviser Jake Sullivan said.
Mr Putin made his own blunt statement, according to his foreign adviser Yuri Ushakov, telling the US president that “the Russian troops are on their own territory and they don’t threaten anyone”.
Speaking on Wednesday, Ms Truss said: “Last week I visited our troops in Estonia and joined Nato foreign ministers in Riga.
“Together we will send a clear message that any incursion by Russia into Ukraine would be a strategic mistake. As President Biden said, there would be ‘very real costs’ to pay.
“We stand with Ukraine in supporting their security and defence, and helping them become more energy independent. Later today, I will be meeting my Ukrainian counterpart Dymtro Kuleba to strengthen our ties further.”
The Foreign Secretary said the UK was already providing support to the country and added there would “high economic and diplomatic costs” to meet any further aggression.
Prime Minister Boris Johnson and other European leaders took part in talks with Mr Biden on Tuesday evening following the meeting with Mr Putin.
It was the second time the five leaders – dubbed the Nato “Quint” – had spoken within 24 hours regarding the diplomatic crisis.
According to Downing Street, the leaders “underlined the importance of Russia ceasing their threatening behaviour towards Ukraine” during the call.
“They agreed on the need for ongoing dialogue with Russia to encourage this outcome,” a spokeswoman said.
“The leaders agreed to stay in close contact and to co-ordinate their approaches to this issue.”