The meeting, prompted by Al-Zarqawi's anger over a lull in terror strikes, led to the spike in violence that has left hundreds dead -- including an Iraqi general killed in a driveby shooting Wednesday -- the military official said.
Al-Zarqawi "wasn't happy with how the insurgency was going. The government was getting stronger and coalition forces not being defeated," the official said, according to accounts of the briefing, which was given on the condition that he not be named.
The Syrian meeting has led to one of the bloodiest periods since the US-led invasion two years ago. Nearly 500 people have been killed since the country's new Shia-dominated government was announced April 28.
Several Shia and Sunni Muslim clerics were among the victims, raising fears that sectarian tensions could ignite a civil war.
Al-Zarqawi seriously wounded: Report
A chilling, rambling Internet audiotape purportedly made by Al-Zarqawi denounced Iraq's Shias as US collaborators and said killing them is justified.
"God ordered us to attack the infidels by all means ... even if armed infidels and unintended victims -- women and children -- are killed together," the speaker said. The tape could not immediately be authenticated.
The Syrian foreign
In response to Al-Zarqawi's order, there have been 21 car bombings, mostly suicide attacks, in Baghdad during May, compared with 25 such attacks in all of 2004, said the senior military official. Nearly 130 car bombs have exploded or been defused since late February, he said.
"The spike [in violence] is a result of the meeting in Syria," the official said. "The folks are listening to what he said."
The disclosures followed comments made by Secretary of State Condoleezza Rice, who during a visit to Iraq on Sunday expressed concern about the "gathering of terrorist networks" in Syria.
Last weekend, US Marines wrapped up an offensive in northwestern Iraq, near the Syrian border, aimed at uprooting sanctuaries for foreign fighters who had crossed into the country.
Al-Zarqawi is Iraq's most-wanted terrorist, responsible for beheadings, assassinations and bombings. The US military has put a $25 million bounty on his head.
His terrorist group, Al-Qaeda in Iraq, also released a statement claiming responsibility for Wednesday's drive-by killing of police Brig. Gen. Ibrahim Khamas in Baghdad. Khamas' wife and driver were wounded, said police Col. Nouri Abdullah. The Internet statement's authenticity was unclear.