It’s a crisis that has divided two Nato members, brought two presidents to loggerheadsand seen the Turkish currency in freefall, but as Foreign Editor David Pratt reports, other deeper grievances lie at the root of the fallout

On the face of it he is the man at the centre of an international crisis. Indicted on charges of espionage, links to terrorist organisations and collaborating with a Muslim sect to overthrow the Turkish government, Andrew Brunson, has soured relations between Ankara and Washington and plunged Turkey into a currency crisis.

Ever since his arrest in 2016 this middle-aged evangelical American pastor and missionary has not only become something of a martyr in the eyes of the US Christian right, but more recently a convenient cause celebre for US President Donald Trump and vice president Mike Pence, the latter sharing Mr Brunson’s evangelical faith.

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The story of Andrew Brunson’s journey to the epicentre of the current diplomatic crisis between the US and Turkey is a peculiar one.

Prior to his arrest Mr Brunson who is originally from North Carolina, ran the small Church of the Resurrection in the western Turkish city of Izmir.

Arrested in the aftermath of the 2016 attempted coup against Turkish president Recep Tayyip Erdogan, he was accused of working with the Fethullah Gulen network, a movement supporting the US-based Turkish cleric that is widely believed to have orchestrated the attempted putsch.

He is also accused of assisting the outlawed Kurdistan Workers Party (PKK), which both Ankara and Washington list as a “terrorist” organisation.

As Mr Brunson’s cause was subsequently picked up by evangelicals in the US, political pressure began to grow, and Washington attempted to cut a deal with Turkey, the Trump administration subsequently dissuading Congress from immediate sanctions on Ankara.

By September of last year though, Mr Erdogan sought to use the pastor as a bargaining chip in Ankara’s long-running battle to secure the extradition of alleged coup plotter Mr Gulen.

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“You have a pastor too,” the Turkish president told the Americans. “Give him to us. Then we will try Brunson and give him to you.”

The Trump administration refused to play on the deal and dug in its heels. The culmination has been the current spat that has divided two Nato members, caused a war of words between two firebrand presidents, and seen the Turkish economy plummet.

Right now this is how the situation stands, and on the face of it, Mr Brunson remains seemingly at the core of the crisis. But there are other much deeper diplomatic, geo-political and economic factors at play here too.

Last week Mr Erdogan in a New York Times op-ed outlined his country’s grievances toward the US, making clear that unilateral actions against Ankara by Washington would only undermine American interests and force Turkey to look for other friends and allies elsewhere.

It was a scarcely veiled threat and one that did not go down well at the White House. It came too against a backdrop of even more complex tensions between the two nations.

Chief among these are arms deals, sanctions on Iran and Turkey’s increasingly ambivalent role in the US and western fight against the self proclaimed Islamic State (IS|) group in Syria.

To take the arms deals first, right now Washington is none to happy at Ankara’s plans to buy the S-400 advanced air-defence system from Russia.

Should Turkey do so, it would mean it both operating the F-35, the newest high-tech jet in the American military inventory, while depending on Russia for maintenance and spare parts for the S-400.

Such a scenario would put Moscow in the position to glean valuable intelligence on how to detect the US plane. Already Turkey has paid $1billion for the aircraft, but a delegation of US senators told Mr Erdogan in no uncertain terms during a visit to Ankara last month that the US Congress would block the transfer of the F-35s if his country deployed the Russian S-400.

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The tension with the US around the arms deals issue has only been compounded of course by Mr Erdogan’s increasing diplomatic courting of Russia and threats to Washington of looking for allies elsewhere.

Which brings us then to the second of the three main grievances between the two countries, sanctions imposed on Iran. With the Trump administration having declared it will block any country that defies the measures it has recently taken over renewed sanctions on Iran, Turkey is faced with a difficult decision.

According to analysts at the US based independent intelligence group Stratfor, given that Iran is almost entirely dependent on imports to meet its fossil fuel needs, the return of sanctions on Iranian energy exports will mean either falling in line with the US or facing the consequences from Washington.

Given the current mood between them it’s extremely unlikely that the Trump administration would even consider granting Turkey a waiver to continue importing oil and gas from Iran. Given too that Ankara’s relations with other potential suppliers such as Iraq and Saudi Arabia are so bad, it leaves Mr Erdogan in something of a bind.

Which brings us to the last of the three most pressing issues rankling both countries. For some time now the Turks have been further complicating the US fight against the jihadists of IS by forcing Washington into protracted negotiations on the use of the crucial Incirlik Air Base that sits on Turkish soil.

Even worse, Ankara working in conjunction with Syrian armed Islamist groups, has launched incursions into northern Syria taking cities like Afrin and targeting Washington’s Kurdish allies.

Only this month Amnesty International reported that Turkish forces are giving these same Syrian armed groups free rein to commit serious human rights abuses against civilians in Afrin. For his part too Mr Erdogan has even gone so far as to threaten US troops operational in the area alongside Kurdish forces.

Yesterday against this bitter backdrop Turkey’s battered lira weakened more than 6 per cent against the dollar, after another US warning that Ankara should expect more economic sanctions unless it hands over detained American pastor Andrew Brunson.

Whether Mr Erdogan decides that such a concession is necessary remains to be seen. Even should he make such a gesture though, there is more than enough bad blood between him and Mr Trump to guarantee other and possibly even more serious showdowns ahead.