By Robin Emmott and Renee Maltezou
BRUSSELS/ATHENS (Reuters) - European leaders played down a Greek threat on Friday not to sign off on final agreements at an EU summit on migration and Britain's membership of the bloc unless Athens wins assurances that EU states will not shut borders.
The Greek gambit came after Austria infuriated EU peers on the eve of the summit by insisting on capping the number of migrants it takes - a move that threatened to clog up the route for migrants leaving Greece to head for Germany and other wealthier EU nations, exacerbating Athens' migration crisis.
"EU at a critical crossroads: without solidarity, without sharing burdens and responsibility, it faces the risk of reaching a dead-end," Greek Prime Minister Alexis Tsipras said in a tweet.
Earlier, a government official told Reuters Greece could not agree to the conclusions "unless there is a clear statement ... that there won't be any unilateral (migrant) action until the next summit. No borders should close until then."
On the face of it, the Greek migration move risked complicating already delicate talks on Britain's renegotiation of its terms with the EU. However, EU officials and leaders played down the significance of the move.
"It would be a mistake to mix those two files ... It would be an error to use blackmail," said Belgian Prime Minister Charles Michel.
The head of the European Parliament, Martin Schulz, also dismissed the idea.
"The Greek government mentioned that nobody should shut their borders otherwise Greece would not agree to Brexit issues. I don't think such package deals are wise," Schulz said, referring to the risk of Britain leaving the bloc.
Austria's move to tighter border controls has been seconded by Slovenia, which plans similar policies in solidarity.
Four sceptical eastern European members have also floated a fallback policy of ring fencing Greece to keep the migrants they expect to land there from proceeding through Macedonia and Bulgaria to other EU countries.
EU leaders decided to hold a special summit with Turkey in early March to make a joint plan to stem the influx work better and said there was no alternative to a common European approach to the migration wave that exposed deep differences in the EU.
The vast majority of migrants and refugees enter the EU in Greece and Athens is fearful that closed borders would leave thousands stranded there.
"It doesn't make sense for Greece, which has made every effort to handle the refugee issue to carry all of the burden and risk being isolated," an official said.
(Reporting by Renee Maltezou in Athens, and by Robin Emmott, Tom Koerkemeier and Andreas Rinke in Brussels; Writing by Paul Carrel; Editing by Ruth Pitchford)