Kiev’s mayor has said Ukrainians will find themselves living in a “nightmare” if Russia invades but insisted his countrymen and women would fight for their future.
Vitali Klitschko sought to counter Moscow’s assertions that Ukraine had sparked the crisis and insisted that his country was “not aggressive to anyone”.
He thanked Britain for offering military and political support to Ukraine and said “it will be very difficult to survive” if that assistance drops off in the event of an invasion.
In an interview with the BBC Radio 4 Today programme, he painted a picture of strong defiance among Ukrainians.
“We are not aggressive to anyone but if someone comes to Ukraine, we don’t have another choice [except to fight],” Mr Klitschko said.
“We have to defend our country, defend our independence, defend our territorial integrity and we have to fight for our country for our values, for our future.”
Asked how Ukrainians would respond if foreign soldiers showed up on their streets, he said: “It will be a nightmare, it will be [an] aggressive attack to Ukraine. We don’t want to do that but we don’t have another choice.”
He said Ukraine is a "friendly nation" that has a vision to build itself up to become a “modern European country”.
Mr Klitschko said Ukrainians have been “shocked” by the build-up of Russian soldiers on the eastern border and on the northern border with Belarus.
His comments come as advisers from Russia, Ukraine, Germany and France prepare to meet for crisis talks in Paris on Wednesday.
Moscow has accused the West of flooding Ukraine with weapons. Nations allied with Ukraine have said Russia is acting as an aggressor.
Before venturing into politics, Mr Klitschko was a world heavyweight boxing champion. He is the only boxer to have held the world champion title in three different decades.
Together with his younger brother Wladimir, they were considered to be the dominant world heavyweight boxers of their era, when their careers peaked between 2004 and 2015.
Mr Klitschko this week accused Germany of “betraying” Ukraine over its support for the Nord Stream 2 gas pipeline and its refusal to supply arms to Kiev.
Writing in German daily newspaper Bild, he said: “There is huge disappointment in Ukraine that the federal government is sticking to Nord Stream 2 and that it does not want to supply defence weapons.
“This is failure to provide assistance and betrayal of friends in a dramatic situation in which our country is threatened by Russian troops from several borders.”
The Kiev mayor said Germany needs to send “clear signals” to Europe and the wider world revealing exactly where it stands on the Ukraine crisis.
“It pains me to see how [Russian President Vladimir] Putin sympathisers” are calling the political shots in Germany, he said.