Greece has delayed the implementation of a historic EU-Turkey deal that aims to stem the flow of refugees fleeing war and conflict in the Middle East.

Key points: Key part of EU-Turkey migrant deal was due to take effect from midnight on Sunday

Key part of EU-Turkey migrant deal was due to take effect from midnight on Sunday But Greece says it needs more time to implement the deal

But Greece says it needs more time to implement the deal Amnesty International says the move is a blow to human rights

Amnesty International says the move is a blow to human rights Around 1,500 people crossed Aegean Sea to Greece's islands in past 24 hours

Under the agreement clinched between Brussels and Anakara on Friday, asylum seekers who reach the Greek islands will be deported back to Turkey. For every Syrian returned, the EU will resettle one from a Turkish refugee camp.

The deal aims to strangle the main route used by asylum seekers travelling to the EU and discourage people smugglers, but it has faced criticism from rights groups and thousands took to the streets of Europe in protest.

Greek premier Alexis Tsipras told his ministers on Saturday afternoon (local time) to be ready to begin deporting people on Sunday, as agreed, but officials have now said they need more time to prepare.

"The agreement to send back new arrivals on the islands should, according to the text, enter into force on March 20," migration policy spokesman Giorgos Kyritsis said.

"But a plan like this cannot be put in place in only 24 hours."

Around 1,500 people crossed the Aegean Sea to Greece's islands on Friday before the deal was brought in, more than double the day before and compared with just several hundred per day earlier in the week.

Hundreds of security and legal experts are set to arrive in Greece to help with implementing the deal, described as "Herculean" by the head of the EU's executive arm.

Refugees and migrants arrive in the port of Greece's Lesbos after crossing the Aegean sea from Turkey in February. ( AFP: Aris Messinis )

Mr Tsipras said with over 40,000 asylum seekers already in Greece, the debt-hit country could not take on this new task without major assistance from its European partners — including the immediate deployment of 2,300 experts.

"Four hundred experts in asylum, 400 interpreters and translators and 1,500 security specialists," Mr Tsipras said, detailing the assistance to be sent to manage the deal.

But Greek officials said they were still waiting for the extra personnel, and without them they would struggle to enforce the new accord.

"We still don't know how the deal will be implemented in practice," a police source on the island of Lesbos said.

"Above all, we are waiting for the staff Europe promised to be able to quickly process asylum applications - translators, lawyers, police officers - because we cannot do it alone."



Deal is a historic blow to human rights: Amnesty International

In total some 4,000 border officials and other experts will be needed to carry out the agreement that will cost the EU up to $444 million over six months.

The assistance includes experts who can address the concerns of rights groups who fear the scheme could fail to protect the rights of those refugees, mainly from Syria and Iraq, to seek asylum.

Amnesty International has called the deal a "historic blow to human rights."

But EU officials have stressed that each application for asylum will be treated individually, with full rights of appeal and proper oversight.

A boat carrying refugees and migrants arrives on a Greek island, after crossing the Aegean sea from Turkey in February. ( AFP: Aris Messinis )

AFP