Turkey's president on Friday slammed the United States for not standing firmly against a failed military coup and accused it of harboring the man he says was the plot's mastermind, as a government crackdown in the coup's aftermath strained Turkey's ties with key allies.

Turkey has demanded the United States extradite Fethullah Gulen, a cleric living in self-imposed exile in Pennsylvania whom it accuses of being behind the violent July 15 coup attempt that left 290 people dead. It is accusing Western nations of not extending sufficient support to its efforts to counter further threats from followers of the Gulen movement, which it says have infiltrated the country's state institutions.

Turkey considers Gulen's movement a terrorist organization. Gulen has denied any prior knowledge of the plot and says his movement espouses interfaith dialogue. The United States has asked Turkey for evidence of his involvement, and said the U.S. extradition process must take its course.

"Instead of thanking this nation that quashed the coup in the name of democracy, on the contrary, you are taking sides with the coup plotters," Turkish President Recep Tayyip Erdogan said in an angry speech Friday at a police special forces headquarters in Ankara. The facility was bombed and fired upon during the attempted coup, and 47 police officers were killed.