From the BBC:

Militants in Pakistan pose a threat to the country's existence, according the the American General, David Petraeus.

Speaking in London after meeting the UK Prime Minister, Gordon Brown, the commander of US Central Command said Pakistan had to deal with the problem.

He went on to say he would help Pakistan make a a sustained commitment to deal with the militants.

His comments come amid tension between the US and Islamabad over American attacks on militants inside Pakistan. ...

"They (Pakistan) clearly have a threat," he said, "the nature of which and the importance of which is increasingly being recognised by those in Islamabad."

"You have heard the newly elected President Zadari. You've heard the army chief and others all recognise that this is in a sense an existentialist threat, this is a threat to Pakistan's very existence," the general added.