The Gülenist Terror Group (FETÖ) remains a thorn in U.S.-Turkish ties as Ankara seeks a more active role from Washington in the fight against terrorism.

Yet, the arrest of a U.S. Consulate employee for alleged ties to the group behind the July 15, 2016 coup attempt, may complicate things. As the employee remains in detention, the United States Embassy in Ankara issued an unusually harsh statement denouncing the arrest, although stopped short of answering the allegations of espionage and terrorism against the employee identified as M.T.

Working as a contact officer at the U.S. Consulate, the suspect contacted FETÖ-linked former Police Chiefs Yakup Saygılı, Nazmi Ardıç, Mahir Çakallı and Mehmet Akif Üner, Anadolu Agency (AA) reported. He also made phone calls to Zekeriya Öz, a fugitive prosecutor who was allegedly behind a string of sham trials by FETÖ to imprison its critics.

The U.S. Embassy denounced the allegations as baseless and claimed that the suspect was "tried in the media rather than a court of law." The strongly worded statement underlined that the arrest may undermine U.S.-Turkish relations while it avoided addressing the charges against M.T., who had multiple phone calls with jailed FETÖ suspects.

M.T. was arrested on Wednesday after his detention last Saturday as part of an Istanbul-based investigation. Media outlets reported that he was detained for espionage and attempting to overthrow the constitutional order, a terrorism charge FETÖ members face, for his contacts with the group's alleged infiltrators in law enforcement.

Öz, one of M.T.'s contacts, is believed to be in Germany after he fled Turkey, faces life terms in Turkey for involvement in two coup attempts perpetrated by FETÖ members in 2013. Çakallı is a former deputy police chief for Istanbul who coordinated the December 2013 coup attempt disguised as police operations. He is among thousands of police officers jailed for links to the terrorist group. Nazmi Ardıç, then head of the Organized Crime Unit in Istanbul, and Saygılı, then head of the Department for Financial Crimes, were both arrested for their links to FETÖ. Üner, another of M.T.'s accused contacts, was the head of the Istanbul Police's Fraud Division during the 2013 attempt. Like M.T.'s other contacts, all were users of ByLock, an encrypted messaging app used by FETÖ that the judiciary has decided can constitute the sole evidenced to prove suspects' ties to the terrorist group.

Media reports say that M.T. assisted FETÖ-linked police chiefs in handing over documents regarding the 2013 police operations to Preet Bharara, a former New York U.S. attorney who conducted an investigation into Reza Zarrab, an Iranian-Turkish national who has been held in the U.S. for three years after being included in a 2013 probe involving people close to the government in Turkey.

This is not the first time that staff members of a U.S. mission are in the limelight for what the Turkish media calls "dubious contact" with FETÖ-linked figures.

Before Adil Öksüz, one of masterminds of July 15 coup attempt last year, dumped his cellphone and disappeared, he received one last call from an Istanbul telephone number. Someone from the U.S. consulate called the theology lecturer to inform him that his visa application had been canceled, according to U.S. Embassy claims. The call went unanswered and the whereabouts of Öksüz are unknown. According to investigators, the U.S. Consulate placed a call to Öksüz while he was on the run. Recently, government spokesman Deputy Prime Minister Bekir Bozdağ called on the U.S. to clarify the matter regarding Öksüz, "[s]o that there will not be other scenarios being talked about."

Ankara has repeatedly asked the United States to extradite FETÖ leader Fetullah Gülen and, at one point, to arrest him to prevent his escape, but officials complain of the slow process in the case. Ankara says "85 boxes of concrete evidence" were sent to U.S. judiciary officials about Gülen and his network's culpability in the coup attempt. Most fugitive FETÖ members have been seen in the U.S.

Although Turkey and the United States enjoy strong relations highlighted by the close friendship of their presidents, lack of action against FETÖ in the United States overshadows it.

Strong anti-American sentiments have persisted in Turkey, especially after the coup attempt, with recent surveys showing that social media is awash with comments denouncing the perceived role of the U.S. in the coup bid. Even though conspiracy theories linking the U.S. to past coups in Turkey are nothing new, it is Gülen, the leader of FETÖ, whose stay in the U.S. is fueling rumors. Gülen has been a resident of the country since 1999, and currently lives in a posh retreat in Pennsylvania where he frequently gives interviews to the media.

On Wednesday, AA reported that a key coup suspect was confirmed to be associated with Gülen due to a document from the U.S. Department of Homeland Security. The document, sent to Turkish authorities in September, affirmed that Batmaz, one of masterminds of the putsch bid, was lying when he told a court he did not meet Gülen. It shows that Batmaz stayed at Gülen's residence. At least this was what he said when he was interviewed by U.S. officials in New Jersey when he arrived in the United States some six-and-a-half months before the coup attempt.

Batmaz and Öksüz, two civilians, are believed to have directed soldiers on behalf of FETÖ. Both were caught by CCTV cameras at the 143rd Fleet at Akıncı Air Base, the command center for the coup attempt, on the night of July 15. Öksüz managed to flee after a controversial court ruling ordered his release, while Batmaz was jailed. According to the official document – time stamped Jan. 1, 2016 – Batmaz told American officials who questioned him at New Jersey's Newark Airport that he "will stay with Imam Fetullah Gülen in Pennsylvania" during his visit to the country.

The document, which was sent by the Department of Homeland Security to the Turkish General Directorate of Security on Sept. 8, and delivered as evidence to the 17th High Criminal Court of Turkey trying Batmaz, is one of the most important pieces of evidence that directly links the coup attempt to Gülen. Batmaz, a former executive of Kaynak Kağıt, a paper company that operated one of the largest business conglomerates affiliated with the terrorist group, told a court trying him and dozens of others last August he was near Akıncı to see a plot of land he planned to purchase in the company of Harun Biniş, another employee of a FETÖ-linked company.

"The United States will continue to engage with the government of Turkey to ensure that employees of the U.S. government, as well as American citizens in Turkey, are accorded due legal process in accordance with the Turkish constitution and international legal norms. For decades, the tireless work of local employees of both countries to promote cooperation between Turkey and the United States has improved security for both of our countries, enhanced business opportunities and brought our citizens closer together. Baseless, anonymous allegations against our employees undermine and devalue this longstanding partnership," the U.S. Embassy's statement added.