WASHINGTON, March 3 (Xinhuanet) -- US President George W. Bush said Thursday that stopping Osama bin Laden from a new attack on US soil was "the greatest challenge of our day."

    Bush confirmed reports that bin Laden had asked his chief ally in Iraq Musab al-Zarqawi to launch attacks in the United States when attending a public swearing-in ceremony for Homeland Security Secretary Michael Chertoff.

    "Bin Laden's message is a telling reminder that al Qaida still hopes to attack us on our own soil," Bush said. "Stopping him is the greatest challenge of our day."

    Bush has vowed to hunt down bin Laden since the Sept. 11 terrorist attacks in 2001, but Laden is still now at large and occasionally reveals video or audio tapes to show his existence. The US intelligence agencies believe Laden is hiding in the border region between Afghanistan and Pakistan.

    "We're on a constant hunt for bin Laden. We're keeping the pressure on him, keeping him in hiding," Bush said.

    "We're working every day and night to dismantle his network and to bring him to justice," he said.

    A US counterterrorism official told reporters on Monday that bin Laden asked al-Zarqawi to include the United States as his terrorist attack target. US State Department spokesman Brian Roehrkasse said earlier that the intelligence about the continued al Qaida desire was "credible but not specific." Enditem