President of the European Council Donald Tusk has confirmed all EU leaders have reached an agreement with Turkey's prime minister to curb the migration crisis.
The new arrangements could come into force as soon as Sunday after a revised deal was reached between Turkish PM Ahmet Davutoglu and European Council president Donald Tusk in Brussels.
Royal Navy ship RFA Mounts Bay is being deployed to tackle people smugglers bringing migrants across the Aegean Sea.
The amphibious landing ship will use an onboard Wildcat helicopter to provide information to the Turkish coastguard.
It is hoped that officials will then be able to intercept boats attempting the perilous crossing to Greece.
The ship will join naval vessels from Germany, Canada, Turkey and Greece as part of Nato's first intervention in the migrant crisis.
Two Border Force cutters will also join the operation, along with a third boat - the chartered civilian vessel VOS Grace - which is already in the Aegean.
The agreement involves closing the EU border on March 20 and sending back migrants who arrive in Greece after that date to Turkey.
Cameron asks EU leaders to back deployment of more international patrol ships close to Libyan coast in bid to deter migrant smugglers.
David Cameron will tell his European colleagues that the migration route from Libya to southern Italy is about to begin once more.