Britain on Friday said it "must be prepared for the worst" as Greece risks exiting the eurozone in the absence of a deal over bailout repayments.
"We have entered the eleventh hour of this Greek crisis, and we urge the Greek government to do a deal before it is too late," Chancellor of the Exchequer George Osborne said in a statement ahead of a meeting of EU finance ministers in Luxembourg on Friday.
"We hope for the best, but we now must be prepared for the worst," he said.
Britain, though not a member of the eurozone, counts the neighbouring bloc as its main trading partner.
Chancellor of the Exchequer Osborne said Britain had already taken measures to increase its "economic security" from risks abroad.
"And clearly now we must go on and complete that plan," he added.
Greek Prime Minister Alexis Tsipras has said Greece's exit from the eurozone would be the beginning of the end of the single currency.
In an interview published Friday in Austrian newspaper Kurier, he insisted that the Greek government is unable to absorb austerity imposed upon it by the EU and the International Monetary Fund.
The comments were published after talks between finance ministers and Greece fell apart in Luxembourg Thursday, leaving Athens with less than two weeks to unlock billions of euros in bailout funds to service its debts.