"Pakistani and Afghan militant groups -- Tehrik-e Taliban Pakistan (TTP), the Haqqani Network, and Lashkar-e Taiba (LeT) - continue to pose a direct threat to US interests and our allies in the region, where these groups probably will remain focused," said Matthew G Olsen, Director of the National Counterterrorism Centre.
In his written testimony during a Congressional hearing,Olsen said over the past several years, sustained counter-terrorism pressure has systematically degraded Pakistan-based al-Qaeda's leadership and operational capabilities.
"These efforts have left the group at its weakest point in the last ten years. Although core al-Qaeda remains committed to its overarching goals, it is clearly a group in decline," he said.
Noting that operationally, the core al-Qaeda has not conducted any successful operation in the West since the 2005 London bombings, the group, however, remains committed to striking Western targets, including the US, Olsen said.
The group's degraded capabilities will compel operational planners to place a greater emphasis on smaller, simpler plots
that are easier to carry out against soft targets, he said.Other South-Asian terrorist outfits, including LeT,continue to post a threat to US and its allies in the region, he said.
Olsen said LeT leaders have maintained a regional focus and the group provides training to a wide range of Pakistani and Western militants, some of whom could plot terrorist attacks in the West without direction from LeT leaders.
"LeT members, frustrated with the group's focus on South Asia likewise, could leave the group to join a more globally focused group such as al-Qaeda. LeT leaders almost certainly recognise that an attack on the US would bring intense international backlash upon Pakistan and endanger the group's safe haven there," he said.
Olsen said LeT has demonstrated its intent to attack Western interests in South Asia in pursuit of its regional objectives, as it did through a high-profile operation targeting hotels frequented by Westerners during the Mumbai attacks in 2008.
The Haqqani Network, he said, continues high profile attacks in Afghanistan and has conducted multiple strikes against NATO and Afghan Government targets, notably the 18-hour multi-pronged assault against military and government facilities in Kabul and three other cities in April.
Earlier this month, Secretary of State Hillary Clinton had notified Congress of US intent to designate Haqqani Network as a Foreign Terrorist Organisation under the Immigration and Nationality Act and as a Specially Designated Global Terrorist Entity under Executive Order 13224.
"Moreover, we remain concerned by the Haqqani Network's ability to provide facilitation and safe haven for local and global groups such as al-Qaeda and to enable these groups to influence one another," he said.
The TTP's claim of responsibility for the August 16 attack on Pakistan?s Kamra air base and its threatening to target coalition supply lines through Pakistan underscore the danger the group poses in the region, Olsen said.
TTP leaders have repeatedly threatened attacks against the US, particularly after the death of Bin Ladin in May 2011. TTP's claim of responsibility for the failed Times Square bombing in May 2010 demonstrates its willingness to act on its intent, he said.