The tapes were secretly recorded by a paid informant testifying against James Cromitie and three other men who were arrested in 2009 on their way to the synagogues.
The informant, Shahed Hussain, met Cromitie in 2008 after being sent by the FBI to infiltrate a Newburgh, N.Y., mosque. While wearing a wire, he later taped conversations they had during meals at restaurants and in meetings at his home.
"Muslims want to take the U.S. down," Cromitie says on one tape played for the jury. "Believe me, we can do it with our regular Muslims here."
Cromitie also bemoans American military ventures in the Middle East.
"What do we do to make it stop?" he says. "We start taking things down here, you understand?"
He adds: "I will kill 10 million (Jews) before I kill one Muslim."
Cromitie, 43, and three men recruited as lookouts - Onta Williams, 34, David Williams, 29, and Laguerre Payen, 28 - have pleaded not guilty to charges of conspiracy to use weapons of mass destruction and conspiracy to acquire and use anti-aircraft missiles to kill U.S. officers and employees.
Prosecutors allege that with Hussain's encouragement, the men hatched the scheme to blow up two synagogues in the Bronx with remote-control bombs. They also wanted to use surface-to-air missiles to shoot down planes at the Air National Guard base in Newburgh, a city north of New York City.
The men obtained what they thought were explosives and a missile system but were actually inert devices supplied by the FBI, prosecutors said. They were arrested on May 20, 2009, when they went to the synagogues to plant the fake bombs.
The defense claims the men were entrapped by Hussain, a 53-year-old Pakistani immigrant who helped the FBI make hundreds of hours of video and audio tapes of the defendants that are the centerpiece of the case.
On tape, Hussain advises Cromitie that to be a good Muslim, he can't kill out of anger toward Jews. However, he says, dying for "the cause" of Islam is righteous.
"It must be in jihad," he says.