The head of the European Commission made a last-minute offer to try to persuade Greek Prime Minister Alexis Tsipras to accept a bailout deal he has rejected before a referendum on Sunday which EU partners say will be a choice of whether to stay in the euro. EU and Greek government sources said Jean-Claude Juncker had offered to convene an emergency meeting of euro zone finance ministers on Tuesday to approve an aid payment to prevent Athens defaulting, if Tsipras sent a written acceptance of the terms.