Latest al-Qaida tape signal to attack?

Latest al-Qaida tape signal to attack?
U.S. intel studying unusual pattern of Zawahiri's words

Fearing a possible coded signal to attack, U.S. intelligence and law enforcement officials are studying an unusual pattern of words in the latest audiotape from al Qaeda's No. 2 man, Ayman al Zawahri.

On the tape, posted on the Internet Wednesday, Zawahri repeats one phrase three times at the end of his message.

Have I not conveyed? Oh God be my witness.

Have I not conveyed? Oh God be my witness.

Have I not conveyed? Oh God be my witness.

A new FBI analysis of al Qaeda messages warns that "continued messages that convey their strategic intent to strike the U.S. homeland and U.S. interests worldwide should not be discounted as merely deceptive noise."

Intelligence analysts are also investigating technical clues that Zawahri's most recent audio message was phoned in via computer phone, using voice over Internet Protocol, or VoIP.

The ease and frequency of Zawahri's propaganda messages is one of the factors that have led U.S. intelligence analysts to worry abut a possible attack against the United States this summer.

The new FBI analysis, reviewing more than 70 al Qaeda messages over the last 14 years, found a recurring theme of "the duty to kill Americans -- both military and civilian."