"We know that much of the training and the direction for terrorists comes from Pakistan and the border area with Afghanistan," Clinton told reporters at the Foggy Bottom headquarters of the State Department.

It has always been a concern, Clinton said when asked about several cases of home grown terrorists in the country.

"We know we've got to work more closely with both Afghanistan and Pakistan to try to root out the infrastructure of terrorism that continues to recruit and train people who are willing to do what is alleged with Zazi, David Headley, and others in the recent cases that have come to light," Clinton said.

Headley, a US national of Pakistani origin was arrested by the FBI in October on charges of planning terrorist attacks in India and Mumbai.

The FBI in its charge-sheet filed this week has accused Headley of being involved in the Mumbai terrorist attacks.

"One of the reasons why President Obama made the decision which he announced last week with respect to our strategy going forward is because we continue to see a syndicate of terrorism that al-Qaida is, in effect, the head of that is not only an aspirational or ideological head, but providing funding and training and equipping and operational direction to a number of terrorist groups," Clinton said.

"And therefore, we will remain very vigilant at home," she said.