A man wearing dark glasses and an Arab headdress wrapped around his face claims to be an American member of Al Qaeda (search) and promises attacks that will make the streets of America "run red with blood" in a video aired Thursday night by FOX News.

"The magnitude and ferocity of what is coming your way will make you forget all about September 11th. ... After decades of American tyranny and oppression, now it's your turn to die. Allah willing, the streets of America will run red with blood, matching drop for drop the blood of America's victims," the man, calling himself "Azzam the American," says on the tape.

A U.S. official told FOX News the tape is believed to be authentic. But the CIA (search) says it has been unable to confirm the tape's authenticity and is analyzing it further.

The tape bears the logo of the As-Sahab Production Committee (search), which has produced previous Al Qaeda tapes.

FOX News obtained the videotape independently of ABC News, which also aired portions of the video Thursday night.

News broke Wednesday that ABC had the tape and had provided it to federal officials, but the network decided not to air it immediately because a preliminary CIA analysis was unable to determine if it was legitimate.

The tape was handed to the CIA and National Security Agency by ABC News three days ago, multiple government sources told FOX News. ABC is said to have received the tape last weekend from a terrorist source in Waziristan, a region in Pakistan near the Afghan border where the Taliban and Al Qaeda are believed to be holed up.

"We cannot verify the authenticity of this tape," one official said after the preliminary technical analysis presented inconclusive results. One source said the verification process had been complicated because the tape is a copy, not an original.

In the 75-minute message, the speaker praises the Sept. 11 attacks, calls Usama bin Laden and his deputy his leaders, and says a new wave of attacks could come at any moment.

The speaker claims the United States is his country of origin but does not say specifically where he lives. He speaks both Arabic and English with an international accent that is hard to characterize, an intelligence official said.

"The video content is classic Al Qaeda propaganda, in terms of anti-U.S. ideology and denunciation of the U.S.," a U.S. official told The Associated Press.

The official also said the video appears to have been made in the last several months, perhaps as recently as late summer, because of references to the conflict in Darfur, Sudan, and the Sept. 11 commission.

Some U.S. officials speculated that the voice might belong to Adam Yahiye Gadahn, a 25-year-old Southern Californian fingered by the FBI for possible ties to Al Qaeda. Gadahn also goes by the names Adam Pearlman and Abu Suhayb Al-Amriki.

In May, the FBI announced that Gadahn had ties with senior Al Qaeda lieutenant Abu Zubaydah in Pakistan, and that he had attended terrorist training camps in Afghanistan and served as a translator for the terror network.

According to a U.S. official, the tape is being shown to detainees to help identify the speaker.

FOX News has learned the FBI will send the tape to its field offices as early as Friday, hoping agents can press their sources for information about the video's origin and "Azzam the American."

The Associated Press contributed to this report.