Pakistan is probing possible links between militant groups on its soil and the New York bomb plot as US media said evidence was mounting that the Pakistani Taliban were involved.
Faisal Shahzad, the 30-year-old son of a retired air force officer who migrated from Pakistan and became a US citizen last year, has been charged with five counts of terrorism for trying to bomb Times Square on Saturday night.
According to the US criminal complaint, he admitted to receiving bomb-making training in Waziristan, a hotbed of Taliban and Al-Qaeda linked militants with increasingly overlapping associations and ideology.
Here are the main groups:
-- Tehreek-e-Taliban Pakistan (TTP)
Pakistan's premier national security threat and headed by Hakimullah Mehsud, who has wielded a ruthless ambition to oversee a dramatic escalation in bloodshed and ally with Al-Qaeda.
The faction has claimed or been blamed for some of the most daring attacks during a nearly three year bombing campaign across Pakistan.
Mehsud appeared in a video alongside the Jordanian Al-Qaeda double agent who killed seven CIA agents in an attack in Afghanistan in December 2009, lending credence to a TTP claim to have been involved in the attack.
The group has threatened attacks on major US cities to avenge a US drone war that killed its founder, Baitullah Mehsud. The faction claimed the failed New York bomb plot, but the move has been discredited by many.
Al-Qaeda has masterminded attacks on civilian and military targets in various countries, the most notable being the September 11 attacks in 2001.
The group operates globally, with strongholds in Pakistan and Afghanistan.
It trademark tactics are spectacular bombings causing maximum carnage.
The White House says the group is turning to smaller, "less sophisticated" attacks as a result of US action since late 2001.
Banned in Pakistan, the organisation was formed in 1994 with the primary aim to secure independence for Kashmir, claimed by India and Pakistan.
The group emerged after supporters of Maulana Masood Azhar split from another Islamist militant organisation, Harkat-ul-Mujahideen.
Azhar is wanted in India over the hijacking of an Indian airliner in 1999.
The group features on the US list of terrorist organisations and adheres to the same ideology as the Taliban.
One of Pakistan's most feared outfits and banned by the government. The Sunni Muslim group was formed in 1996 when its founder, Riaz Basra, broke from Sipah-e-Sahaba Pakistan (SSP).
The organisation has links with Al-Qaeda and the Taliban.
Basra has been dead for a number of years. Reports differ on whether he was killed in an explosion or a shootout with security forces.
It was among several groups involved in the kidnap and beheading of Wall Street Journal reporter Daniel Pearl in January 2002.
The group has earned notoriety for its relentless suicide bombings and gun attacks on Pakistan's minority Shiite Muslims.
-- Lashkar-e-Taiba (LeT)
LeT is one of the most active Pakistan-based militant organisations which has concentrated on fighting Indian rule in Kashmir, but is thought to have some ties to the Taliban and Al-Qaeda.
It was blamed for the November 2007 Mumbai attacks. The group is blacklisted by the United States and United Nations, and banned by Pakistan.
It was founded by Hafiz Mohammad Saeed, who now heads Jamaat-ud-Dawa, a charity wing considered a front of LeT but which was feted in Pakistan for its charity work after the October 2005 south Asian earthquake.
-- Haqqani network
Presided over by anti-Soviet mujahedeen commander Jalaluddin Haqqani and effectively led by his son, Sirajuddin Haqqani.
Its leadership is based in North Wazirsitan, but its decentralised cell structure has close ties to the Taliban and Al-Qaeda.
It is seen as one of the toughest US foes in eastern Afghanistan and its members have been targeted by US drones.