Pakistani authorities have busted an American-born al Qaeda leader, officials said yesterday.

But it's not clear which one.

The captured terrorist may have been Adam Gadahn, 31, a Californian who converted to Islam, moved to Afghanistan, and became al Qaeda's flack.

In 2006, he became the first American charged with high treason since the end of World War II.

Or it might be Abu Yahya Mujahedeen Al-Adam, a turncoat who commanded terrorist fighters in Afghanistan.

Little is known of Al-Adam, except that he was born in Pennsylvania.

The similarities between the names "Adam" and "Al-Adam" may be responsible for the confusion.

But it is clear that an American was arrested in Karachi, Pakistan, and has since been moved to Islamabad for questioning.

Gadahn, who was home-schooled by his hippie parents on a goat farm, released his latest video calling for attacks on America the same day he may have been captured.

"You shouldn't make the mistake of thinking that military bases are the only high-value targets in America and the West," he said, praising last year's attack at Fort Hood.

"On the contrary, there are countless other strategic places, institutions and installations [where], by striking, the Muslim can do major damage."

The reported arrest of an American traitor follows the recent detention of several Afghan Taliban commanders in Karachi, including the group's No. 2.

"If this is [Gadahn], it's a big capture and a morale-booster," said Patrick Rowan, the former top anti-terrorism official in the Bush Justice Department.

As al Qaeda's spokesman, he has appeared in more than half a dozen of its videos, taunting the West and calling for its destruction.

"It's a blow to al Qaeda and a boost to the US when a guy that has been taunting the US for years has been captured," Rowan said.

The arrest was made in Karachi in recent days, two officers who took part in the operation told the AP.

Intelligence officials said the suspect was being interrogated by Pakistani officials. It was not clear if any Americans were involved in his capture or questioning.

In the past, Pakistan has handed over some al Qaeda suspects arrested on its soil to the United States.

If the man in custody is indeed Gadahn and authorities can get him to talk, he could offer valuable intelligence about al Qaeda's second-in-command, Ayman al-Zawahiri, and maybe even Osama bin Laden, Rowan said.

Gadahn, who could face the death penalty, has been on the FBI's most wanted list since 2004, and there is a $1 million reward on his head.

In addition to treason, he faces two counts of providing material support to a designated foreign terrorist organization.

He moved to Pakistan in 1998, according to the FBI, and is said to have attended an al Qaeda training camp six years later, serving as a translator and consultant.

Al Qaeda has used Gadahn as its chief English-speaking spokesman. In one video, he ceremoniously tore up his American passport. In another, he admitted his grandfather was Jewish, ridiculing him for his beliefs and calling for Palestinians to continue fighting Israel. With Post Wire Services