Angela Merkel’s top adviser on Europe dismissed threats by Turkish leader Recep Tayyip Erdoğan to pull out of the EU’s refugee deal with Ankara as "bluster," according to leaked British diplomatic cables.

Erdoğan, who has vowed to upend the refugee pact if the EU doesn’t make good on its promise to grant Turks visa-free travel, has a greater interest in keeping the deal alive than allowing it to collapse, Merkel adviser Uwe Corsepius told a senior British diplomat in Berlin, according to the diplomatic cables seen by POLITICO.

“Uwe Corsepius told me today that the EU should remain calm,” the British diplomat reported back to London on May 13. “While Erdoğan still had the ability, in theory, to generate a surge in the refugee flow, his threats were just bluster. It was in Erdoğan’s strategic interest to keep the relationship with the EU working.”

The Corsepius cable was signed WOOD, suggesting it was written by Sebastian Wood, the British ambassador to Berlin.

Europe cut a deal with Ankara in March to provide billions of euros in aid, and grant Turkish citizens a visa waiver as early as this summer, in exchange for Turkey’s commitment to reduce the flow of refugees heading to Europe.

Since then, Turkey has signaled it wouldn’t accept a European requirement to reform its controversial anti-terror laws, sparking a heated back-and-forth between Ankara and European capitals.

Though little known outside of official circles, Corsepius — who previously served the senior-most civil servant at the Council of the European Union in Brussels — plays a key role in shaping Merkel’s European policies and has been deeply involved in negotiations with Turkey.

The Corsepius cable was written before recent tensions emerged this month between Berlin and Ankara over the German parliament’s decision to declare the Ottoman Empire’s 1915 massacre of Armenians a genocide.

Nonetheless, the communication helps explain Merkel’s tempered response to Ankara’s persistent taunts. The cable suggests Berlin has concluded that Erdoğan needs Europe just as much as Europe needs Turkey.

“EU accession and visa liberalization remained strategic goals for Turkey,” the diplomat paraphrases Corsepius as saying.

Berlin’s strategy is to draw the process out, in part to allow the tempers on both sides to calm. “We can keep this under control,” Corsepius adds, according to the cable.

Georg Streiter, a spokesperson for the German government, told POLITICO that he was not familiar with the cables in question.

Refugee numbers down

“Absolutely nothing has changed regarding the German position,” Streiter said, referring to the EU-Turkey deal.

Indeed, despite the heated rhetoric, Turkey has continued to honor its end of the bargain. The number of refugees crossing the Aegean to Greece has declined sharply in recent months.

To keep the deal alive, Berlin would likely be willing to grant Turkey further concessions, the British diplomatic cable concludes.

“Despite the tough public line, there are straws in the wind to suggest that in extremis the Germans would compromise further to preserve the EU/Turkey deal,” the cable says. “Officials have shown some interest, behind the scenes, in thinking about possible compromise formulations on the anti-terror law.”

About 1.5 million Turks currently have “special passports,” which are supposed to be for officials, civil servants, teachers and their families, the Sunday Times reported.

The batch of cables, which include a detailed analysis of how the U.K. should position itself on the Turkey question, offers a rare, unfiltered glimpse of the behind-the-scenes diplomatic maneuverings between Europe’s capitals. A spokesman for the U.K. foreign office said the telegrams were "reports from our diplomatic posts, not statements of British government policy.”

One of the cables, sent from the British embassy in Ankara on May 5, sparked controversy in the U.K. after being leaked to the Sunday Times.

The telegram suggested that to keep Erdoğan on-side, the U.K. government should consider setting up its own visa-free scheme, dropping travel restrictions for Turkish “special passport” holders. About 1.5 million Turks currently have such passports, which are supposed to be for officials, civil servants, teachers and their families, the paper said.

The suggestion was jumped on by the Brexit campaign as evidence of secret negotiations to open the U.K.'s borders to Turks — an allegation furiously rejected by Downing Street.

Karnitschnig reported from Berlin and McTague from London. Janosch Delcker contributed to this article.