The United States on Friday said it was concerned over the Al Qaeda's [Images] 'gaining strength' in the northern frontier of Pakistan and a 'lot of intelligence' suggesting that there are ongoing efforts to plan an attack against America.

US Secretary of State Condoleezza Rice, speaking to the Fox News, maintained that the terror network has lost its strength 'on quite a few dimensions' in the post-9/11 period.

'They have been losing strength on some dimensions -- quite a few dimensions -- as they lose more and more of their financial network, as they lose more and more of their ability to operate freely in countries with which we are now aligned.'

However, she said, 'I think it's true that in the frontier areas of Pakistan, this has been a period in which we have been concerned about their gaining strength.'

'But there are puts and takes. It is not as if this is an organisation that has gotten stronger and stronger so that they are now back to the point they were on September 11.'

Asked to comment whether she shared the feeling of the Homeland Security Secretary that this is a particularly dangerous time for the US in terms of its vulnerability to an attack or the possibility of an attempt to mount one, she said, 'I am certainly concerned about it.'

'It is a period of time in which there is a lot of intelligence, a lot of chatter that would suggest that there is an effort to plan an attack against the United States... there is nothing that appears concrete or imminent. But we always have to be vigilant.'

'It is a kind of unfair fight. The terrorists have to be right once and we have to be right 100 per cent of the time,' Rice said.

The Secretary of State also pointed out that the Al Qaeda has always been trying to regroup.

'I don't think that one can make the argument that Al Qaeda is the same organisation that it was on September 11th. You cannot lose a whole layer of field generalship in the way that they have, you cannot lose your training bases in Afghanistan, you cannot lose the capacity to freely move money around because there is no effort at tracing terrorist financing,' she said.

'What they have done, of course, is they have continued to try to reconstitute,' Rice said.