"I would welcome an urgent opportunity to discuss with concerned governments new collaborative arrangements, within and outside the EU, to ensure predictable and safe disembarkation of those rescued at sea," he says.

Grandi says both the UNHCR and International Office for Migration (IOM) will soon come forward with a plan that encapsulates the ideas. Both currently operate programmes in Libya and Niger to resettle refugees and return people back home.

The letter, dated 18 June, is addressed to Bulgaria's prime minister Boyko Borisov, whose country is at the helm of the six month EU presidency.

The IOM has previously confirmed it was working with the UNHCR for handling the new sea arrivals ideas - but only within the European Union, noting "nothing has been finalised yet."

Outside or inside EU?

Such efforts come amid leaked draft of the EU summit conclusions, which mentions setting up so-called "regional disembarkation platforms", where migrants would be filtered in an effort to stop sea journeys towards Europe.

"Platforms are here to stay, this is a debate that Europe is discussing with interest," said one senior EU official.

But it remains unclear what such platforms would look like in practice, their legal implications, and where exactly they would be set up.

The EU in 2015 launched so-called 'hotspots', defined at the time as a means to relocate genuine asylum seekers arriving in Italy and in Greece elsewhere in Europe.

Such zones, particularly on the Greek islands, have caused untold grief and suffering for thousands stranded in overcrowded centres, described by some as open prisons, where women and children fear abuse and sexual violence.

The three scenarios

As for the disembarkation ideas being floated, three scenarios have emerged.

The first option is a regional arrangement with coastal states in north Africa countries. People rescued at sea would then be offloaded in countries outside Europe. Those in need of protection are shuffled into a resettlement programme run by the UNHCR, while everyone else is sent home by the IOM.

The second option entails regional arrangements between EU countries. This includes identifying people in need of protection and involves a beefed up European border and coast guard agency, also known as Frontex, and a bigger European asylum support office (Easo).

Both agencies are set to get an extra boost following soon-to-be announced proposals by the European Commission, which also includes stepping up returns.

The third option, which has been dismissed by the European Commission, would involve sending rejected asylum applicants to centres outside the EU.

"None of these options, none of them have been explored right to the end. There are two that can provide fertile ground for discussions," said Natasha Bertaud, a European Commission spokeswoman, in Brussels on Monday (25 June).

Bilateral deals

The ideas on disembarkation are designed, in part, to address Italian demands to stop people from reaching its shores.

But Germany is more concerned with preventing asylum seekers from then travelling freely across its borders, in what is known as secondary movements.

The two priorities clashed ahead of a mini-summit on migration in Brussels on Sunday, billed as one that aims to find European solutions, but where Germany then supported plans for direct deals with other EU states.

"There will be bilateral and trilateral agreements, how can we help each other, not always wait for all 28 members," Angela Merkel, Germany's chancellor, said on Sunday, in a nod to her supposed ally and interior minister, the Christian Social Union's Horst Seehofer.

Seehofer had given Merkel a two-week deadline over threats to impose bilateral deals, regardless of her opposition, to stop and turn back asylum seekers at Germany's internal border.

The European Commission now appears ready to back such direct deals.

It says existing EU asylum laws allow for one EU state to speed up returns of asylum seekers under the Dublin regulation, which determines who is responsible for processing claims for international protection.

"What is possible under EU law is for member states to conclude bilateral arrangements, trilateral arrangements, to accelerate the procedures that are contained in the Dublin regulation including 'take back, take charge requests'," said Bertaud.