WASHINGTON — Federal officials charged two American women, who they described as supporters of violent jihad, with conspiring to build and plant bombs in the United States as part of a terror attack, the Justice Department announced Thursday.

Noelle Velentzas, 28, and Asia Siddiqui, 31, discussed how to build an explosive device with an undercover officer but hadn't specified targets, according to a criminal complaint unsealed in federal court Thursday.

The two New York women were roommates in Queens until recently and allegedly had been planning to build an explosive device since at least August 2014, the complaint read. They are held without bail after they appeared Thursday afternoon in federal court, where they said they understood the charges, The Associated Press reported.

"My client will enter a plea of not guilty, if and when there is an indictment. I know it's a serious case but we're going to fight it out in court," said Siddiqui's lawyer Thomas Dunn, while Velentzas' attorney had no comment, AP reported.

ABC News first reported the arrests and noted the charges come after a lengthy FBI operation.

According to the complaint, the women espouse "violent jihadist beliefs" and expressed interest in terrorist attacks committed within the United States. Velentzas is described in the complaint as having praised the Sept. 11, 2001 attacks and referred to Osama bin Laden and his mentor as her heroes, and once stated that she and Siddiqui were "citizens of the Islamic State."

The women allegedly researched how to develop bombs with items such as pressure cookers, which were used in the Boston Marathon bombing. The complaint read that Siddiqui has multiple propane gas tanks and instructions on how to turn them into bombs, and that she had repeated contact with members of al-Qaida.

But it's unclear how much progress the women made in learning how to build bombs, the complaint said.

U.S. Attorney Loretta Lynch, President Barack Obama's nominee for U.S. Attorney General, is prosecuting the cases.

"As alleged, the defendants in this case carefully studied how to construct an explosive device to launch an attack on the homeland," read a statement from Lynch. "We remain firm in our resolve to hold accountable anyone who would seek to terrorize the American people, whether by traveling abroad to commit attacks overseas or by plotting here at home."

If convicted, the women could face life in prison.

The New York women's arrests come on the same day as news that an American citizen — once thought to be a top al-Qaida operative — had been secretly flown from Pakistan to New York to face federal terrorism charges.

And just last week, the FBI disrupted a plot to kill scores of people at a U.S. military installation involving an Illinois Army National Guardsman and his cousin, who were charged with attempting to provide material support to the Islamic State.

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