Two New York women pleaded guilty on Friday to charges they studied how to make bombs for a terrorist attack on U.S. soil., federal prosecutors said.

Asia Siddiqui, 35, and Noelle Velentzas, 31, were "inspired by radical Islam" and taught each other chemistry and electrical skills necessary to build explosives and detonating devices, Assistant U.S. Attorney John Demers said in a statement. The women also researched how to make plastic explosives and car bombs to carry out attacks similar to the Boston Marathon and Oklahoma City bombings, as well as the 1993 attack on the World Trade Center, authorities said.

Siddiqui and Velentzas pleaded guilty in Brooklyn federal court to one count of teaching and distributing information pertaining to the making and use of an explosive, destructive device, and weapon of mass destruction, intending that it be used to commit a federal crime of violence. The women each face up to 20 years in prison, but the term could be shorter under sentencing guidelines and with credit for the more than four years they’ve already been behind bars awaiting trial. They are due to be sentenced in December.

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"Velentzas and Siddiqui were intent on waging violent jihad here in the United States, researching at length historical terrorist attacks on U.S. soil, educating themselves on how to turn propane tanks into explosive devices, and dreaming up plans to kill Americans on our own turf," FBI Assistant-Director-in-Charge William F. Sweeney Jr. said in a statement.

The pair were arrested in 2015 as part of a sting operation in which a New York Police Department officer working undercover wore a wire and posed as a convert to Islam. The pleas ended the prospect that the women’s trial would provide a rare glimpse into how the NYPD uses informants and undercovers to smoke out Islamic extremists - a method long criticized by civil rights groups who say it risks luring harmless people into phony plots. Police officials had expressed concern that the officer’s cover could have been blown if she had to testify.

“In an effort to implement their violent, radical ideology, the defendants studied some of the most deadly terrorist attacks in U.S. history, and used them as a blueprint for their own plans to kill American law enforcement and military personnel,” U.S. Attorney Richard P. Donoghue said in a statement. “Thanks to the tireless work of law enforcement, they were stopped before they could bring their murderous plans to fruition.”

The women used the teachings of radical jihadist Samir Khan, who was a prominent member of Al Qaeda but is now deceased, as inspiration for their plots. Federal prosecutors say Siddiqui submitted writings to the magazine.

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Similarly, Velentzas "espoused violent rhetoric, praising the attacks of Sept. 11, 2001, and stating that being a martyr through a suicide attack guaranteed entrance into heaven." She also specifically singled out government and law enforcement targets stating, “you go for the head” when you commit a terrorist attack.

“This investigation and the subsequent guilty pleas are yet another example of how each day the NYPD and members of the Joint Terrorism Task Force remain vigilant and relentless in their efforts to protect New York City and keep America safe,” NYPD Commissioner James P. O’Neill said. “I want to commend our law enforcement partners and the U.S. Attorney’s Office for the Eastern District for helping to bring these individuals to justice.”

The Associated Press contributed to this report.