Bush has signed into law the most sweeping overhaul of US intelligence in nearly 60 years, aiming to remedy broad failures that led up to the September 11 terrorist attacks.

“Under this new law, our vast intelligence enterprise will become more unified, coordinated and effective. It will enable us to better do our duty, which is protect the American people,” he said during a signing ceremony.

The legislation, which grew out of the formal investigation into the terrorist strikes of 2001, creates a director of national intelligence to oversee the agenda and the budgets of the 15 US intelligence agencies.

“A key lesson of September the 11th, 2001, is that America’s intelligence agencies must work together as a single, unified enterprise,” said the president, who did not put forward a nominee for the post.

“Those charged with protecting America must have the best possible intelligence information. And that information must be closely integrated to form the clearest possible picture of the threats to our country,” he said.

The legislation, which Bush likened to the 1947 law that created the Central Intelligence Agency and the US Defence Department, creates a national centre to integrate and analyse all US intelligence on terrorism.

A spokesman for President Bush, Scott McClellan, said the White House was already considering candidates to fill the new post.

The move came as US officials said they had authenticated a new audiotape by terrorist mastermind Osama bin Laden, in which he called on his fighters to strike Gulf oil supplies and warned Saudi leaders of an uprising.

It also followed the embarrassing withdrawal of Mr Bush’s nominee to head the Department of Homeland Security, Bernie Kerik, who officially said he was bowing out because he thought he may have employed an illegal immigrant.

The White House has yet to announce a replacement, but speculation has centred on outgoing Secretary Tom Ridge’s deputy, Asa Hutchinson, or homeland security adviser, Frances Townsend.

At the signing ceremony, the president was surrounded by lawmakers who helped craft the bill as well as the chairmen of the commission that probed the 2001 attacks on the World Trade Centre and the Pentagon.

President Bush initially opposed the creation of the panel and refused to testify before it, and also initially did not endorse giving broad budget authority to a director of national intelligence.

Also present were CIA Director Porter Goss, who faces internal opposition to his efforts to overhaul the agency, and FBI chief Robert Mueller, as well as relatives of people killed in the September 11 attacks.

Some critics of the legislation have doubted that the national director will have the clout necessary to manage intelligence agencies while simultaneously trying to change the way they operate.

Others have noted that the legislation went forward well before a final report from the commission charged with investigating why US intelligence failed to recognise that there were no weapons of mass destruction in Iraq.

The president, who also initially fought against the creation of the Department of Homeland Security, noted that he was signing the legislation in the same room where NATO was created by treaty.

“America, in this new century, again faces new threats. Instead of massed armies, we face stateless networks. We face killers who hide in our own cities. We must confront deadly technologies,” he said.

“To inflict great harm on our country, America’s enemies need to be only right once. Our intelligence and law enforcement professionals in our government must be right every single time,” he said.

“Our government is adapting to confront and defeat these threats,” said Mr Bush.