Back from a visit to Russia, Prime Minister Alexis Tsipras will meet his negotiating team in Athens and may speak to European Commission chief Jean-Claude Juncker by phone to try to break the deadlock before an emergency summit on Monday. With nervy depositors pulling billions out of Greek banks, Athens may have to impose capital controls within days to staunch the flow. While Greece has dug in its heels over demands for pension cuts and some tax rises, its leaders have continued to sound upbeat about the chances of reaching a deal — optimism that is not widely shared among Europe’s leaders.