* Johnson and Varadkar to meet in England

* Johnson: cautiously optimistic

* EU tells Britain: Make more concessions

By Elizabeth Piper and Guy Faulconbridge

LONDON, Oct 10 (Reuters) - Prime Minister Boris Johnson will meet his Irish counterpart on Thursday in a last-ditch attempt to revive a British proposal for a Brexit deal that the European Union said falls far short of what is needed for an orderly divorce.

Just three weeks before the United Kingdom is due to leave the world's biggest trading bloc, it is still unclear on what terms it will leave or indeed whether it will become the first sovereign state to depart the European project.

Brexit descended into a public row between London and Brussels this week after a Downing Street source said a Brexit deal was essentially impossible because German Chancellor Angela Merkel had made unacceptable demands.

The EU accused Johnson of playing a "stupid blame game" and bluntly told London on Wednesday - exactly a week since Johnson's initial bid for a last-minute deal - that it would have to make further significant concessions.

As both sides position for another delay followed by a British election, or an acrimonious divorce on Oct. 31, Johnson will meet Irish Prime Minister Leo Varadkar at an undisclosed location in the north west of England on Thursday.

"This will be a private meeting to allow both leaders and their teams to have detailed discussions," the offices of both leaders said in identical statements.

Johnson said he was cautiously optimistic, though Varadkar said on Tuesday that it would be very difficult to strike a Brexit deal by next week - when the EU holds a crucial Oct. 17-18 summit.

"They're seriously focused on trying to resolve this issue and trying to get a deal," junior business minister Kwasi Kwarteng said.

EU diplomats, though, are sceptical about the chances of a deal. Most expect Johnson to be forced to accept a delay to Brexit - a step that could ultimately lead to either a disorderly exit or the reversal of the entire Brexit endeavour.

(Writing by Guy Faulconbridge; editing by Alistair Smout)