US intelligence agencies expect the Al Qaeda [Images] to post a new video on the internet urging its cadres to mount biological, chemical and nuclear attack on the West, reports ABC News.

While there is no evidence of a direct threat, the Federal Bureau of Investigation has nevertheless alerted some 18,000 law enforcement agencies across America, ABC News has reported.

FBI spokesperson Richard Kolko told ABC News in an email that 'there have been several reports that Al Qaeda will release a new message calling for the use of weapons of mass destruction against civilians.'

'The FBI and US intelligence community will review the message for any intelligence value.'

However, there are many who think the public need not worry itself silly over the threat.

Like Ben Venzke, CEO of IntelCenter which monitors terrorist communication on the web, who thinks the new video is done by a jihadi supporter and not part of the Al Qaeda's official communication.

'Supporter videos are made by fans or supporters who may or may not have had any contact with a real terrorist,' Venzke told ABC News. 'Considering them to be [an official video] would be equivalent to considering a 10-year-old's homemade fan video as the official team message.'

That may be so, but what worries the intelligence community enough to take the threat seriously is that the new video comes on the heels of a clutch of messages from Al Qaeda's number two, Ayman al-Zawahiri.

Just a couple of weeks earlier, on Israel's 60th anniversary, the Al Qaeda released an audio message from bin Laden � the fourth from his this year -- abusing countries supportive of Israel.

None of this, however, worries FBI director Robert Muller too much. 'There is a difference between Al Qaeda's ability to communicate internally and its ability to post a message on the internet. As we all know, the internet is so broad, the access is absolutely open that anybody can post material on it,' Muller said earlier this month.