The White House says it is enacting the measures to fight international terrorist groups and prevent the spread of weapons of mass destruction.

The authorities will also be given the power to seize the property of people deemed to be helping the spread of WMD. An independent commission recommended the measures earlier this year.

The new measures form part of Mr Bush's overhaul of US intelligence agencies, aimed at bolstering the fight against terrorism and weapons proliferation.

FBI overhaul

The FBI is to be re-organised, and will include another new intelligence body called the National Security Service.

It will assume responsibility for intelligence work within the US, and combine the Justice Department's intelligence, counter-terrorism and espionage units.

Correspondents say the measure is designed to help dissolve the barriers between the FBI and the CIA.

John Negroponte, who was given the new job of US director of national intelligence in April, will be charged with putting the changes into effect.

Other measures include:

An executive order allowing US authorities to seize the assets of any person or any company thought to be aiding the spread of WMD, targeting specifically eight companies including two from North Korea, one from Iran and one from Syria

The establishment of a national counter-proliferation centre, to centralise US efforts to stop the spread of nuclear, chemical and biological weapons

Giving control of all overseas human intelligence operations to the CIA

Seeking the creation of a new assistant attorney general position to centralise responsibility for intelligence and national security at the Justice Department.

'Win for the people'

The Silverman-Robb Commission handed its report to Mr Bush in March.

The commission found that US intelligence on Iraq's WMD had been wrong, and it recommended to the president 74 ways in which the US intelligence effort could be improved.

Mr Bush has now accepted 70 of those recommendations.

White House homeland security adviser Frances Townsend said the new measures were a "win for the American people".

"A stronger, more vibrant intelligence community produces better intelligence products upon which good decisions can be made," she said.

Democrats gave a cautious welcome to the measures.

"The FBI will not get ahead of the terrorist threat if it doesn't have a fully dedicated intelligence service, and now it will," California Representative Jane Harman told CNN.

"But this will require a massive culture change within the FBI, because the guns and badges and the mind-set of the FBI don't totally fit with the challenges of countering terrorism."

The BBC's Adam Brookes in Washington says Americans have long resisted the growth of domestic intelligence agencies, believing they pose a threat to civil liberties.

But Mr Bush can ill-afford politically to see another intelligence failure like that in Iraq on his watch, he says.