(CNN) Former New York City Mayor Rudy Giuliani said Wednesday that Hillary Clinton "could be considered a founding member of ISIS" because she was secretary of state during the Obama administration's withdrawal from Iraq.

Giuliani, a Republican, delivered the sharp criticism in an interview on Fox News' "The O'Reilly Factor" during a segment on the Brussels attacks and the Obama administration's response to them. He was quick to link Clinton to what he saw as failures of the administration's response to ISIS.

"She had her chance to (rally people against ISIS) -- she helped create ISIS. Hillary Clinton could be considered a founding member of ISIS," Giuliani said.

Pressed by host Bill O'Reilly, Giuliani explained his reasoning.

"By being part of an administration withdrew from Iraq. By being part of an administration that let (Iraqi Prime Minister Nouri al-Maliki) run Iraq into the ground, so you forced the Shiites to make a choice. By not intervening in Syria at the proper time. By being part of an administration that drew twelve lines in the sand and made a joke out of it," Guiliani said.

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