America's topmost military officer has sounded the alarm on new terrorist attacks, and said the Al Qaeda [Images] threat from Pakistan is the biggest challenge facing his country, the Washington Post reports.

Adm Michael Mullen, chairman of the US joint chiefs of staff, said despite the scale of threat, progress would be slow since Pakistan has been lagging behind in its strategy to eliminate safe havens for terrorists in the lawless Federally Administered Tribal Areas.

Part of the problem was Pakistan's complex tribal allegiances and sensitivities over sovereignty issues that tied up America's hands in acting against any threat. 'It is going to take longer than most people realise,' Adm Mullen told newspersons.

Mullen also said Pakistani authorities need to enforce any deal struck with the tribal leaders in FATA, and called on them to include in any deal the expulsion of Al Qaeda and halt the flow of insurgents into Afghanistan.

Worryingly for Pakistan, the US is reported to have told Islamabad that if it suffered another terror attack which can be traced back to Pakistan, then it will have no option but retaliation. The new Pakistan ambassador to Washington, DC, Husain Haqqani, confirmed this, and added, 'We want to make sure it doesn't come to that. Pakistani preference remains to not have outside forces' action.'

According to Haqqani, any new deal with the insurgents will have the following terms: the fighters will promise not to launch attacks in Pakistan and Afghanistan; they will expel all foreign fighters from the tribal areas; they will decommission large weapons and use smaller ones.

And on America's insistence, Haqqani said, the fighters will also have to promise not to provide a safe haven to anyone targeting Pakistan's allies, including the US.

Asked which of the insurgent groups will accept such demands, Haqqani said there 'reconcilable people' in the groups who will be willing to 'subscribe to the conditions in return for benefits.'