Senior U.S. intelligence officials said yesterday that they think the English-speaking al Qaeda associate who warned of new terrorist attacks against the United States on a recently released videotape is Adam Yahiye Gadahn, a Californian in his mid-twenties who converted to Islam in 1995.

But an FBI spokesman said the bureau is not ready to conclude that the man, whose face was wrapped in a headdress on the videotape, was Gadahn.

In May, Attorney General John D. Ashcroft and FBI Director Robert S. Mueller III announced that Gadahn, who left California for Pakistan in 1998, is a supporter of al Qaeda who has translated documents for the group. He was among seven people they said authorities were seeking out of increased concern that they could plan, facilitate or take part in terrorist attacks against the United States.

"We have some confidence, but not certainty, that the voice is that of Gadahn," an intelligence official said yesterday, referring to the videotape that was dropped off at an ABC News office in Pakistan about two weeks ago.

The man on the tape -- who said in accented English that his name was "Azzam the American" -- warned that new attacks on the United States could be launched "at any moment."

"My fellow countrymen, you are guilty, guilty, guilty, guilty," he added. "You are as guilty as Bush and Cheney. . . . 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."

FBI spokesman Ed Cogswell said yesterday that "we haven't reached any conclusions about the tape. The FBI is not even leaning in the direction that it's Gadahn." After Gadahn's parents were shown the tape by the FBI they were uncertain whether it was their son, whom they have not seen for about six years, he said.

"They're iffy," Cogswell said. "They don't want to commit."

A Muslim cleric in Orange County, Calif., who knew Gadahn in the 1990s has told reporters that he believes the man on the tape is Gadahn because of what he believes are similarities in voice and gestures. Haitham Bundakji, an imam at the Islamic Society of Orange County, has said he was assaulted by Gadahn, an incident that led to Gadahn's firing as a mosque security guard.

Gadahn is the son of a Muslim butcher and grew up being home-schooled in a rural area of Southern California. After years of adolescent searching and an obsession with "demonic" heavy-metal music, he converted to Islam in 1995, according to a posting bearing Gadahn's name on a Web site in the late 1990s.

A man seen in a tape warning of new attacks against the United States may be Adam Yahiye Gadahn, at right in an undated photo.