The recent communications indicated bin Laden has "encouraged Zarqawi and his group to focus on attacks inside the United States."
U.S. officials would not get into detail about how the communication was made or how it was intercepted by the United States. They also said that there is nothing specific in the message, such as maps or references to particular cities or buildings. Rather, the communication simply encourages a "focus" on attacks inside U.S. borders, sources said.
One homeland security official called the communication "a fairly recent development" and said the threat was still being analyzed.
The Homeland Security Department issued a classified bulletin to officials over the weekend about the intelligence, which spokesman Brian Roehrkasse described as "credible but not specific." The intelligence was obtained over the past several weeks, officials said.
One homeland security official on Tuesday further clarified the classified bulletin that was sent out over the weekend. These bulletins are fairly routine and "law enforcement sensitive" but this one was "classified" and only sent to the homeland security advisors as a "heads up" about the new intelligence.
"It's not new that Al Qaeda wishes to expand its operations outside of Iraq, especially targeting U.S. interests," one DHS official told FOX News, saying there was no plan to raise the alert level. "We wanted to alert our folks in a timely manner and put the intel in context."
Roehrkasse also earlier said the U.S. has no immediate plans to raise its national alert level but said the intelligence "reiterates the desire by Al Qaeda and its associates to target the homeland."
Al-Zarqawi, the leader of Al Qaeda in Iraq (search) and believed to be the inspiration of the ongoing bombings, beheadings and attacks on Iraqi and American forces, last year changed the name of his group in Iraq to reflect his ties to Al Qaeda. Iraqi officials said they expect to take al-Zarqawi soon; they recently nabbed a key associate and driver of the Jordanian-born terror leader. He has a $25 million U.S. bounty on his head and is known by several other names.
U.S. officials say al-Zarqawi has "his hands full" trying to stay out of U.S. or Iraqi custody in Iraq and they question whether al-Zarqawi's group would have the ability to pull off an attack inside America. Also, officials are wondering aloud what this means about Al Qaeda and whether if the group is reaching out to its central leader because they are under significant pressure.
"My view of that is that we can't dismiss anything these guys say," said Peter Brookes, a former CIA operative and current senior Heritage Foundation fellow. "But Zarqawi has his hands full in Iraq. I think we're going to catch him rather soon. He's hunkered down, he's still able to do attacks, but I think that's where he's going to be focused."
Sen. Sam Brownback, who returned from a trip to Iraq on Monday night, noted that U.S. and Iraqi officials have recently captured several close al-Zarqawi associates and came close to nabbing al-Zarqawi himself.
"Apparently they had him on screen and were gaining in on him but he slipped away so they're getting quite close to him," the Republican senator from Kansas told FOX News on Tuesday. "He seems to be the most actionable person within the Al Qaeda network right now and we need to keep on him."
In October, al-Zarqawi 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.
Another administration official with access to the Homeland Security Department's bulletin said the intelligence indicates that Al Qaeda has continued to encourage al-Zarqawi 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."
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.
Jane Corbin, a Mideast correspondent for the BBC and author of "Al Qaeda: In Search of the Terror Network That Threatens the World," told FOX News that the correspondence between the two terror leaders may mean it's more necessary for bin Laden to outsource terror acts, particularly since his network has been smashed and fractured since the War on Terror began and he has little freedom to operate in any country now.
"The fact he [bin Laden] is talking to him [al-Zarqawi] shows, I think, that he needs to spread the net, he needs to get others to do the work for him," Corbin said.
But al-Zarqawi has also been under pressure in Iraq, she noted, particularly since the U.S.-led offensive last year in the terror hotbed of Fallujah destroyed his base in Iraq.
"Since that's been taken back, it's believed he's had to move north and into the Mosul areas," Corbin said. "He's still a force to be reckoned with ... [but] he's got his hands full just surviving in Iraq"
"Although I'm sure bin Laden would like to involve al-Zarqawi in how he'd like to attack the American mainland, realistically, what can he do because he's still on the run in Iraq."
Last year, the Jordanian government also stopped an al-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 (search) 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."
FOX News' Bret Baier, Catherine Herridge, Liza Porteus, Nick Simeone and The Associated Press contributed to this report.