The EU and Turkey have agreed the broad principles of a plan to ease the migration crisis at a summit in Brussels, but delayed a final decision.
European Council President Donald Tusk said irregular migrants arriving in Greece would be returned to Turkey.
For each Syrian migrant returned, Turkey wants the EU to accept a Syrian refugee, and offer more funding and progress on EU integration.
Talks on the plan will continue ahead of an EU meeting on 17-18 March.
Hopes for EU-Turkey migrant deal
