Senior UN official has warned number of people stranded in Greece could quickly double from 32,000

Turkey is under growing pressure to consider a major escalation in migrant deportations from Greece, a top European Union official said on Thursday, amid preparations for a highly anticipated summit of EU and Turkish leaders next week.

European Council President Donald Tusk ended a six-nation tour of migration crisis countries in Turkey, where 850,000 migrants and refugees left last year for Greek islands.