Washingon, Apr. 7 : The United States has once again raised concerns over the Pakistan's Inter Services Intelligence (ISI) links with outlawed extremists groups.

In an interview to a private Afghan television channel, US Secretary of Defense Robert Gates said: "The ISI''s contacts with some of the extremist groups like Gulbuddin Hekmatyar, the Haqqani network, Commander Nazir and others are a real concern to us."

Gates said Washington has already conveyed its apprehensions to Islamabad, and it hopes that Pakistan will take the issue seriously.

"We have made these concerns known directly to the Pakistanis. And we hope that they will take action to put an end to it," The Dawn quoted Gates, as saying.

Gates refused to disclose any details regarding the US led drone attacks on militant hideouts in the ungoverned tribal areas along the Pak-Afghan border.

"I can''t talk about our military operations, obviously. But President Obama has made clear that we will go after Al-Qaeda and their planning cells and their training centres, wherever they are in the world," Gates said replying to a question that whether he considers the missile strikes against Pakistan's sovereignty.

Gates also was skeptic about the Swat peace deal, as previous such accords in 2005 and 2006 had resulted in an increase in the number of violent extremists coming across the border into Afghanistan.

He said Pakistan understands that the rising extremism not only poses serious threat to its own stability, but it is also dangerous for the neighboring Afghanistan.

Commenting on the revamped US strategy for the Afghanistan and Pakistan Gates said : "One of our goals in this new strategy is to see how we can improve cooperation between Afghanistan and Pakistan, who have a common interest in getting rid of these extremists."

Gates maintained that Pakistan is one of the important allies of the United States in the `War on Terror', and said that it is prepared to provide weapons and training to enhance Pakistan's counterinsurgency capabilities. (ANI)