The world’s most extreme terrorist groups met twice earlier this year in an effort to set aside their philosophical differences and unite in a new holy war against the United States and Israel, law enforcement officials tell Fox News.

The two meetings, according to the officials, took place in Beirut, Lebanon in February and the Iranian capital of Tehran in late April. The gatherings are described as "unprecedented," and went largely unnoticed in the west. A handful of officials in the White House were briefed on the event.

Dubbed the "Jerusalem Conference" by its 400 or so participants, the group drafted a document pledging to unite behind the Palestinians and win total Arab control over Jerusalem. "The only decisive option to achieve this strategy is the option of Jihad (holy war) in all its forms," the document says, according to law enforcement officials who have seen it. "America today is a second Israel."

The group – made up of Usama Bin Laden’s al-Qaeda, the Palestinians’ Hamas and Islamic Jihad factions, the Lebanese Hezbollah and militants from Egypt, Pakistan, Jordan, Qatar, Yemen, Sudan and Algeria – has named its task ahead, "The Jerusalem Project."

Sources tell Fox News that at least one participant went to the conference from the United States and returned here afterward.

The sources say "The Jerusalem Project" is headquartered in Beirut and led by two men -- Musa Abu Marzouq, a Hamas leader who was in 1977 arrested in New York and later deported to Jordan; and Ramadham Abdullah Shallah of the Palestinian Islamic Jihad, who has two sons that served in Bin Laden's Mujahedin unit against the Soviet's in Afghanistan.

Iran reportedly sent several official diplomats to the meetings, including Hojatoleslam Ali Akbar Mohtashami, a well known Iranian intelligence official.

Carl Cameron currently serves as Fox News Channel's (FNC) Washington-based chief political correspondent. He joined FNC in 1996 as a correspondent.