Turkish groups on Tuesday published a full-page advertisement in the Washington Post newspaper urging U.S. President Donald Trump not to cooperate with terror groups.

The open letter by the Turkish-American National Steering Committee (TASC), which represents nearly 150 nongovernmental organizations (NGOs) based in the U.S., emphasized the strengths of the Turkey-U.S. partnership in security and trade.

The letter was published on the same day that President Trump hosted his Turkish counterpart President Recep Tayyip Erdoğan for their first meeting in the Oval Office.

TASC said the Gülenist Terror Group (FETÖ), which Ankara accuses of being behind the failed coup attempt last summer in Turkey, is "an insidious cult that has also been spreading across this nation disguised in the form of charter schools and intercultural and interfaith associations."

"We urge Americans to exercise great caution," the letter said.

Charter schools linked to FETÖ leader Fetullah Gülen have faced more intense scrutiny since the July 15 putsch attempt.

The Federal Bureau of Investigation (FBI) is leading an investigation into a network of FETÖ-linked charter schools that span 28 states.

City officials in Linden, New Jersey, in March asked state authorities to block the opening of a new FETÖ-linked school on the basis of the school's "fatally flawed" application that contained "forged and fraudulent" documents.

The TASC letter also asked the Trump administration to drop its support for the PKK terrorist organization's Syrian offshoot the Democratic Union Party (PYD) and its armed wing, the People's Protection Units (YPG), which Ankara considers terrorist groups.

The Pentagon announced last week the U.S. would begin directly arming the group in the fight against Daesh.

"The U.S. should support its ally rather than backing a terrorist organization," the letter said.