The European Union is due to approve a further 3 billion euros in funding for Syrian refugees living in Turkey, EU officials said ahead of a meeting with President Recep Tayyip Erdoğan scheduled for later this month.

Despite tense relations in recent years, the EU depends on Turkey to keep a tight lid on illegal immigration from the Middle East, where the war in Syria has killed hundreds of thousands and pushed millions from their homes.

Top EU officials will meet with Erdoğan on March 26 in the Bulgarian city of Varna despite misgivings among many on the European side.

The bloc's top migration official Dimitris Avramopoulos will announce on Wednesday that the European Commission proposes the extra funding on projects benefiting Syrian refugees in Turkey, the sources told Reuters.

Over 1 million refugees and migrants reached the EU in 2015, most of them flowing through Turkey. Brussels agreed to pay to help host migrants on Turkish soil in exchange for Ankara preventing more from trying to cross the Aegean Sea to Greece.

Turkey and the EU signed an agreement on March 18, 2016 to stem the influx of refugees to Europe. Turkey has been a main route for refugees trying to cross into Europe since the beginning of the civil war in Syria. With the agreement, irregular arrivals decreased by 99 percent, saving the lives of those who would have attempted the treacherous journey by sea.

The deal included a 6 billion euro aid package to help Turkey care for the millions of refugees being hosted in the country with an initial 3 billion euro tranche for projects to support Syrian refugees. The deal also included visa-free travel for Turkish citizens to the Schengen Area. However, this has yet to be implemented as relations between Turkey and the EU have been strained and await resolution. Some EU countries' stances toward critical issues for Turkey's national security have further increased the tension. Officials from Ankara have been calling on Europe to give up its weak stance and take Turkey's legitimate concerns into consideration. The EU will also release what the sources said would be a critical report on Turkey's accession bid in April.