From the roads of Pennsylvania and corridors of power in Washington to the public squares of Cologne and EU offices in Brussels, the shockwaves from the July 15 failed coup have gone well beyond Turkey.

The aftermath of the coup that aimed to unseat President Recep Tayyip Erdogan has prompted a drastic sharpening in Turkish rhetoric towards the EU and US, with Ankara saying it feels let down by an apparent lack of solidarity.

Analysts say it would be unlikely for now that Turkey, a NATO member since 1952 and EU candidate for decades, could readjust its pro-Western stance or recalibrate its policy towards traditional rivals like Russia.

But the ferocity of the rhetoric has been unprecedented, with Erdogan Tuesday accusing Turkey's Western allies of supporting the plotters and taking particular offence that Germany refused to let him address a rally in the western city Cologne via video conference.

Erdogan has meanwhile warned Washington it will put relations at stake if it fails to extradite Fethullah Gulen, the Pennsylvania-based preacher who Ankara accuses of being at the heart of the coup plot, charges he denies.

"You have to be blind and deaf not to understand that he is behind all of this," Erdogan said.

Yet to Erdogan's fury, Washington has yet to show any sign of moving against Gulen, insisting Turkey is a key partner while saying Ankara must send evidence and not just speculation.

- 'Not easy going' -

Yet the crisis has erupted at a time when the Ankara-Washington relationship is as important as ever, with the United States needing Turkish help in the battle against Islamic State (IS) militants in Syria.

US fighter jets use Turkey's southern base of Incirlik as a crucial launch point for lethal raids against IS targets in neighbouring Syria.

Extremely worryingly for a base that houses dozens of American tactical nuclear weapons, Incirlik was also a key point in the coup with its Turkish commander arrested and power temporarily shut down.

Meanwhile, the US military has also been unsettled by the sacking and arrest of nearly half of Turkey's generals, and believed to include figures who worked closely with American forces at Incirlik.

But Turkey is still for Washington an "essential partner in the Middle East" and will do all it can to satisfy Ankara "even if they are not going to cede on Gulen", said Jean Marcou, Turkey expert at Sciences Po in Grenoble.

The United States has long experience in handling difficult situations with Turkey, he said. "It's not easy going... there can be problems but that is not going to destroy an alliance and strategic equilibrium."

Turkish media said US Secretary of State John Kerry would visit by the end of the month while joint chiefs of staff chairman General Joseph Dunford came to Turkey for a highly symbolic visit this week.

"Dunford's visit shows the US and Turkey are still bound in a sustainable strategic alliance," said Unal Cevikoz, former Turkish ambassador to London.

- 'Pro-Western strategic axis' -

Relations with the European Union -- which Turkey has sought to join since the 1963 -- could prove even more fraught with top officials in Brussels angering Ankara by raising concerns over the magnitude of the post-coup purge.

Turkey has also grumbled that it has so far not received its promised returns under the landmark deal to stem the flow of migrants to Europe, raising alarm about the future of the deal.

Even more seriously, the Turkish government has raised the possibility of reinstating capital punishment for the coup plotters, a move which would at a stroke doom its EU membership bid.

Austria's Chancellor Christian Kern on Wednesday said the membership talks were "no more than fiction". Turkey has insisted officially that membership remains a key objective.

Having patched up a dispute with Russia over the November shooting down of a Russian war plane, Turkey could be tempted to head into the arms of Russia to counter its problems with the West.

Foreign Minister Mevlut Cavusoglu contrasted the "unconditional support" Ankara received from Moscow in the wake of the coup with other countries and Erdogan will visit Russia for the first time after the bilateral crisis in August.

Yet there remain a litany of problems -- including Syria and Ukraine -- on which Moscow and Ankara can find no harmony and the countries share a regional rivalry that dates back to the Ottoman and Russian Empires.

"There is not a single international crisis on which the Turks and the Russians agree, not one," said a Turkish expert who asked not to be named.

Despite the Turkish rhetoric, "the Turkish-Western alliance will remain the axis on which Turkish foreign policy turns," said Marcou.