U.S. counterterrorism officials say a video of an al-Qaida recruiter threatening to smuggle anthrax across the Mexican border and into the U.S. via an underground tunnel is authentic, The Washington Times reported on Wednesday.

The video aired in February on Al Jazeera and has since appeared on militant Web sites, the paper said, calling it the latest sign that the terror group is determined to carry out another major attack on U.S. soil.

The video shows Kuwaiti dissident Abdullah al-Nafisi telling supporters in Bahrain that al-Qaida is seeking to commit another attack and is even willing to align itself with white extremist groups in the United States.

"Four pounds of anthrax — in a suitcase this big — carried by a fighter through tunnels from Mexico into the U.S. are guaranteed to kill 330,000 Americans within a single hour if it is properly spread in population centers there," the recruiter reportedly said, according to a translation.

"What a horrifying idea; 9/11 will be small change in comparison. Am I right? There is no need for airplanes, conspiracies, timings and so on. One person, with the courage to carry 4 pounds of anthrax, will go to the White House lawn, and will spread this ‘confetti’ all over them, and then we’ll do these cries of joy. It will turn into a real celebration."

Al-Nafisi "is a significant ideological player in terrorist circles, and that makes him dangerous because he can inspire his followers to do extremely bad things," a U.S. counterterrorism official told the Times on condition of anonymity.

A spokesman for Homeland Security Secretary Janet Napolitano said the U.S. takes such threats seriously, the paper reported.

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