The delays on implementation of the so called readmission agreement for third country nationals is a headache for the European Commission and EU states, which want to see it up and running.

The agreement applies to people who are not asylum seekers or refugees but who arrived in the EU from Turkey.

The Turkish parliament approved the deal on 1 June. It was also signed by the president’s office on 18 May and published in Turkey’s Official Journal on 20 May.

But the law still needs to be rubber stamped by Turkey's council of ministers before any EU state can start sending people who do not have the legal right to remain in the EU back to Turkey.

"This decision should be taken as a matter of urgency," said a commission spokesperson in an email to EUobserver.

Bulgaria is also not happy.

A spokeswoman for the Bulgarian mission to the EU said it has people they want to return to Turkey but cannot until Ankara implements the law in full.

"Turkey is our neighbour so of course we are the first to be affected," she said.

Around 200 people are likely to be sent packing from Bulgaria to Turkey when the time comes.

"It's not a significant number but it is a question of principle, this is an agreement between the EU and Turkey," she said.

Visa waivers

Turkey's hesitation may be tied to another EU deal to lift short-term visas on Turks who want to visit a country in the passport-free Schengen area.

The initial plan had foreseen a visa waiver to Schengen states this summer, but was derailed after Ankara refused to amend its tough anti-terrorism laws.

Turkey says the law must remain unchanged due to the recent spate of terrorist attacks, with the most recent assault killing 45 people at the Ataturk airport in Istanbul on 28 June. Three militants from the Islamic State group are said to be behind the slaughter.

Critics say the law is overly broad and is being used to silence opposition MPs and journalists. The EU, for its part, will not budge until the issue, along with a handful of other problems, is first sorted.

In May, political group leaders at the European Parliament announced they would suspend all work on lifting visas until Ankara meets all 72 benchmarks required for the waiver.

No new deadline has since been set, although Turkey's president Recep Tayyip Erdogan had previously announced October as the objective

Erdogan had also threatened to end the EU's migrant swap deal unless the visas were lifted, but later backed down.