President Recep Tayyip Erdogan threatened Friday to open Turkey's borders to allow migrants to reach the EU, in a move that would tear up a landmark deal that has reduced the flow. Erdogan's comments, some of his toughest in recent times against the EU, prompted an immediate warning from Germany which helped broker the deal that such threats were unhelpful.
The threat came a day after the European Parliament angered Ankara by backing a freeze in EU accession talks, already hit by alarm over its crackdown in the wake of the July 15 failed coup.
"Listen to me. If you go any further, then the frontiers will be opened, bear that in mind," Erdogan told the EU during a speech in Istanbul. He said Brussels had cried out for help in 2015 as tens of thousands of migrants massed at Turkey's border crossing with EU member Bulgaria. "You began to ask us 'what will we do if Turkey opens its borders'?" he asked.
On March 18, Ankara and Brussels forged a deal for Turkey to halt the flow of migrants to Europe - an accord that has largely been successful in reducing numbers crossing the Aegean Sea between Turkey and Greece.
According to the International Organization for Migration (IOM), just over 171,000 have crossed to Greece so far this year, much lower than the comparable figure for 2015 of almost 740,000.
Hundreds of migrants drowned while trying to cross the Aegean in 2015 on unseaworthy boats, including three-year-old Syrian Aylan Kurdi. The images of his lifeless body washed up on a Turkish beach spurred the international community into action.
Turkey agreed to step up maritime and land border controls in exchange for incentives on its long-stalled membership bid, including visa-free travel for its citizens and an acceleration of accession talks.
However with an October target passing, no apparent progress on the visa issue and the accession talks stalled, Ankara has accused Brussels of failing to keep its side of the bargain.
In response to Erdogan's remarks, EU Commission spokesman Margaritis Schinas said it would not get involved in "statements about hypothetical scenarios" and was still committed to implementing the agreement.
The analysts say the entire membership process is in deep trouble, with little hope of progress and several risk factors that could lead to its collapse.
"Realistically, moving forward is also nearly impossible... Both Brussels and Ankara remain stuck and are playing for time," Asli Aydintasbas of the European Council on Foreign Relations (ECFR) said in a research paper.
She suggested an alternative form of engagement between Turkey and the EU, other than full membership, could be agreed to save face and move forwards.
"In reality, most officials privately concede that full membership is not a possibility at this point," she said.
Austria's Foreign Minister Sebastian Kurz, a hardliner on Turkey, said Europe should strengthen its own borders after Erdogan's comments and "must not give into blackmail".