Al-Zarqawi, who rivals bin Laden as the nation's public enemy No. 1, has been involved in attacks in the Middle East but has not been known before to have set his sights on the United States.
The message is vague and does not specifically mention the United States, but intelligence analysts believe bin Laden is calling on Zarqawi to go after American targets, reports CBS CBS News National Security Correspondent David Martin.
The Homeland Security Department issued a classified bulletin to officials over the weekend about the intelligence, which spokesman Brian Roehrkasse described Monday as "credible but not specific."
In an earlier message, bin Laden had named Zarqawi the head of al Qaeda operations in Iraq. This latest message, which is about two week old, gives Zarqawi a much bigger mission, reports Martin.
The intelligence was obtained over the past several weeks, officials said.
The United States has no immediate plans to raise its national terror alert level, Roehrkasse said. However, the intelligence "reiterates the desire by al Qaeda and its associates to target the homeland," he said.
Al-Zarqawi is blamed for scores of attacks in Iraq and pledged allegiance to bin Laden and the al Qaeda network last year. Yet he has had differences with bin Laden, and his efforts are considered somewhat distinct from central al Qaeda operations.
An administration official with access to the Homeland Security Department's bulletin said the intelligence indicates that al Qaeda has continued to encourage al-Zarqawi, who was born in Jordan, to get involved in terrorist actions against Americans outside of Iraq — including in the United States.
"The intelligence continues to be analyzed by the intelligence community and all appropriate information will be passed on to homeland security partners," Roehrkasse said. "The department has no plans at this time to raise the threat level based on this nonspecific information."
DHS sent the bulletin to state homeland security directors. A Justice Department official said the FBI was not involved, and that the information that led to the bulletin was gleaned by CIA intelligence.
Al-Zarqawi has a $25 million U.S. bounty on his head and is believed to have orchestrated a wave of car bombings, kidnappings, assassinations and beheadings across Iraq. He has run an increasingly dangerous, but diffuse, network of operatives in Iraq known by a number of names. Al-Zarqawi is blamed largely for attacks in the Middle East, including numerous attacks in Iraq and foiled plots targeting U.S. and Israeli targets in Jordan at the millennium.
In October, he made a first-ever pledge of loyalty to bin Laden, by posting a message on a Web site known for carrying militant Islamic content. At the time, U.S. officials believed al-Zarqawi was hoping to appeal to a larger audience and adopt bin Laden's broad objective to attack the United States.
Bin Laden, who is believed to be hiding on the rugged border between Afghanistan and Pakistan, is thought to communicate with his deputies by courier, taped messages and other means. In January 2004, Kurdish forces in Northern Iraq detained one courier, Hassan Ghul, who was carrying a letter written by al-Zarqawi to bin Laden. In it, al-Zarqawi proposed trying to start a civil war between Iraq's Sunni and Shiite Muslim populations.
Last year, the Jordanian government also stopped a Zarqawi-linked plan to use chemicals and explosives to blow up Jordan's secret service agency, the prime minister's office and the U.S. Embassy.
The Jordanians are also after al-Zarqawi, for whom they issued a death warrant and who was convicted last year for assassinating U.S. aid worker Laurence Foley in Amman in 2002.
At a Senate hearing this month, CIA Director Porter Goss warned that al-Zarqawi has "sought to bring about the final victory of Islam over the West." Goss said al-Zarqawi hopes to establish a safe haven in Iraq from which his group could operate against "'infidel' Western nations and 'apostate' Muslim governments."