Kevin James, 31, and Levar Haley Washington, 28, entered their pleas in separate appearances before U.S. District Court Judge Cormac J. Carney. Washington also pleaded guilty to using a firearm to further the conspiracy. Prosecutors said he used a shotgun to rob a Torrance gas station on July 4, 2005.

James faces up to 20 years in prison when he is sentenced March 31. Washington faces up to 20 years in prison on the conspiracy charge and five years to life for the firearms offense when he is sentenced April 28.

Authorities say James, Washington and two others were part of a California prison gang cell of radical Muslims that planned the attacks in the Los Angeles area.

"Homegrown terrorism remains a grave concern to the security of our country, and this cell was closer to going operational at the time than anyone since 9/11," Los Angeles Deputy Police Chief Michael Downing told reporters at a news conference after the two men entered their pleas.

Police uncovered the plot in July 2005 while investigating a string of gas station robberies that authorities say were committed to finance the attacks. Torrance Police Chief John Neu told reporters at the news conference that authorities linked about 10 holdups to the plot.

The plotters were within weeks of being able to carry out an attack, officials said, when they were discovered about two months before the Jewish holiday Yom Kippur.

Washington and James, who arrived in court in chains and prison jumpsuits, said little during their separate hearings. Both men wore goatees and Washington's face was covered in tattoos.

Washington's attorney, Ellen Barry, said outside court that her client decided it was "in his best interests" to plead guilty. James' attorney, Robert Carlin, declined to comment.

Also indicted in the case were Gregory Vernon Patterson and Hammad Riaz Samana. All but Samana, a Pakistani national, are American-born Muslim converts.

Patterson and Samana are charged with conspiracy to levy war against the U.S. government through terrorism, conspiracy to possess and discharge firearms in a violent crime, conspiracy to kill members of the U.S. government uniformed services and conspiracy to kill foreign officials. Patterson is also charged with a robbery count and using a firearm in a violent crime.

U.S. Attorney Thomas O'Brien said Samana has been declared mentally unfit to stand trial and is undergoing psychiatric care at a federal prison facility. Patterson is expected to plead guilty to a terrorism conspiracy charge on Monday.

Prosecutors say the plot was orchestrated by Washington, Patterson and Samana at the behest of James, a California State Prison, Sacramento, inmate who founded the radical group Jamiyyat Ul-Islam Is-Saheeh, or JIS.