As the European Union leaders' summit approaches, diplomats say the bloc is considering allocating 3.5 billion euros ($4.18 billion) for Turkey, which continues to host around 4 million refugees.

The total 5.77 billion euro package for Turkey, Jordan, Lebanon and Syria, which goes to humanitarian projects, not governments, aims to prevent a new refugee influx into the EU and win time until the 10-year Syrian civil war eventually ends.

Turkey hosts some 4 million Syrian refugees and has spent more than $40 billion (TL 345 billion) providing basic services but wants the EU funds to be paid directly to the government in Ankara.

The 27 leaders are expected to support the funding proposal by the executive European Commission at a summit in Brussels on Thursday.

However, unlike a previous 6-billion-euro round of funding that was partly paid for directly by EU governments, the money will come entirely from the EU's common budget and so the European Parliament will need to give its approval.

That is likely to reopen the EU's tortured debate over relations with Turkey, which lawmakers have long accused of stifling media freedoms and imprisoning political opponents without proper trial, which Ankara also denies.

Under the original migration deal in March 2016, Turkey agreed to take back all migrants and refugees who cross the Aegean to enter Greece illegally, including Syrians, in return for more funds. For its part, the EU has promised to scrap the visa requirement for Turks visiting Europe and accelerate Ankara's bid to join the bloc, although all talks have stalled.

EU leaders on Thursday will seek to revive them, offering Ankara "the EU's readiness to engage with Turkey ... to enhance cooperation in a number of areas of common interest," according to a draft of the final summit statement seen by Reuters.

Similarly, European Commission President Ursula von der Leyen said Tuesday that the EU should update the migration deal signed with Turkey in 2016.

"It is important that we continue to support Turkey, with 3.7 million Syrian refugees living there, some of whom have been in Turkey for 10 years," von der Leyen told reporters on a visit to Berlin.

A similar call came from German Foreign Minister Heiko Maas on Monday as he urged the EU to update its migrant deal with Turkey, highlighting the importance of further funding.

"We need an update to our migration cooperation with Turkey," Maas told Die Welt newspaper in comments published Monday.