The European Commission will give conditional approval for Turks to travel without visas to Europe’s passport-free Schengen area.
The move is part of a deal in which Turkey is taking back migrants who have crossed over the Aegean Sea to Greece. But Turkey must still meet EU criteria, and the deal must be approved by the European Parliament and member states.
The EU fears that without a visa deal, Turkey will not control migration.
The large influx of migrants and refugees arriving in Europe from Turkey, and from North Africa, has caused a political crisis among EU states.
A formal announcement from the European Commission is due on Wednesday.
Under the EU-Turkey agreement, migrants who have arrived illegally in Greece since 20 March are to be sent back to Turkey if they do not apply for asylum or if their claim is rejected.
For each Syrian migrant returned to Turkey, the EU is to take in another Syrian who has made a legitimate request.
Under the agreement, Turkey must meet 72 conditions by 4 May to earn access to the EU’s Schengen area by the end of June, subject to full EU approval. Diplomats have suggested that fewer than 10 still need to be met.
Human rights groups question the deal’s legality and argue that Turkey is not a safe place to return people to.
Last month, however, European Council President Donald Tusk said the deal had begun to produce results.
He praised the Turkish government as the best example in the world on how to treat refugees, despite criticism by rights groups of the agreement.
At the same time, Turkish PM Ahmed Davutoglu said his country had fulfilled its part of the agreement and that the issue of the visa waiver for the EU’s Schengen area was vital for Turkey.