The director of the US Federal Bureau of Investigation (FBI) has outlined sweeping structural changes in response to fierce criticism of its performance before and after the terror attacks of 11 September.

Calling the new agency "pro-active, not reactive", Robert Mueller revealed his intention to shift the focus of the FBI away from fighting everyday crime to combating terrorism.

The bureau is only so good as its relationships - especially with our counterparts overseas

Robert Mueller, FBI director

This will involve taking on an extra 1,600 agents, closer ties with the Central Intelligence Agency (CIA) and greater centralisation of counter-terrorist efforts.

"We need a different approach that puts prevention above all others," said Mr Mueller.

"It is of critical importance that we have that connection of dots to prevent another attack."

But critics of the FBI say that more centralisation will not help an organisation whose headquarters committed huge blunders by ignoring important intelligence on last September's attacks.

One of the main criticisms levelled against the bureau concerns claims made by an agent that she was prevented from investigating a man who later became a key terrorist suspect.

Under fire

The shake-up is one of the most far-reaching in the history of the bureau.

US Attorney General John Ashcroft described the plans as "shifting the FBI's structure, culture and mission to one of preventing terrorism".

It places great emphasis on deploying agents in the field - whether nationally or internationally - to improve intelligence-gathering operations, especially with agencies in other countries.

The new FBI will focus primarily on preventing terror attacks

A total of 3,718 agents will be tasked solely with working on counter-terrorism within the FBI, with about 480 agents moving internally from such divisions as narcotics, white collar crime unit and the violent crime squad.

Mr Mueller said that intelligence-sharing between the FBI and its overseas counterpart the CIA was essential.

"The bureau is only so good as its relationships - especially with our counterparts overseas."

The new plans will also strengthen relationships between the FBI's main headquarters and field offices, establishing mobile "flying squads" - agents who specialise in certain intelligence fields and co-ordinate national and international investigations.

And FBI officials in the field will be given more authority to initiate terrorism investigations and undercover operations without clearance from headquarters.

Past mistakes

The restructuring comes after a field agent in Minneapolis complained that the FBI headquarters in Washington ignored information about Zacarias Moussaoui, who is alleged to have been involved in the planning of the 11 September attacks.

An FBI agent warned of terror suspect Zacarias Moussaoui

In her criticism, Coleen Rowley said that agents in Minneapolis repeatedly appealed for a search warrant for Mr Moussaoui's computer after he was arrested at a local flying school.

Their requests were turned down by FBI headquarters, and when they appealed to the CIA for help they were reprimanded for breaking protocol.

The FBI is also under fire for its failure to act on information from field agents in Phoenix, which might have given clues about the terrorist attacks.

Mr Mueller acknowledged the complaints during a recent speech, saying he was now aware that "our analytical capability is not where it should be".