Al Qaeda remained the "pre-eminent terrorist threat" to the United States, especially with its "cooperation" with militants in Afghanistan and Pakistan, the state department says.
In its annual report, the U.S. State Department also said some of al-Qaeda's "affiliates have grown stronger," such as the Yemen-based Al Qaeda in the Arabian Peninsula (AQAP) and al-Shebab based in Somalia.
"Al Qaeda [AQ] remained the pre-eminent terrorist threat to the United States in 2010," the State Department said in its Country Reports on Terrorism 2010.
"Though the AQ core in Pakistan has become weaker, it retained the capability to conduct regional and transnational attacks," it said.
AQ's cooperation with militants based in Afghanistan and Pakistan, it said, "was critical to the threat the group posed."
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The report said "increased resource-sharing between AQ and its Pakistan-based allies and associates such as Tehrik-e Taliban Pakistan (TTP) and the Haqqani Network meant the aggregate threat in South Asia remained high."
The report said TTP gave support to US citizen Faisal Shahzad, who attempted to stage a car bombing in New York's Times Square in May.
And following a bid on December 25, 2009 to bring down an airplane bound for the US city of Detroit, it said AQAP shipped bombs in the cargo holds of several planes in a failed bid to blow them up in October last year.
Al-Shebab "gained strength in 2010," claiming responsibility in July for twin suicide bombings that killed 76 people in the Ugandan capital Kampala, it said. It was the group's "first major attack" outside of Somalia, it noted.
"Al-Shebab's widening scope of operations, safe haven in Somalia, and ability to attract western militants made it a continuing threat to US interests in the region," according to the report.
The report covers 2010, before U.S. forces killed Al Qaeda leader Osama bin Laden in Pakistan in May.
The report also lists Iran, Syria, Sudan, and Cuba as what the United States considers to be state sponsors of terrorism, Radio Free Europe reports.
It said Iran was "the most active state sponsor of terrorism in 2010," and cited "financial, material and logistic support" for militant groups in the Middle East and Central Asia.
The report accused Iran's regime of backing the Palestinian group Hamas, the Palestinian Islamic Jihad and the Popular Front for the Liberation of Palestine-General Command, along with Lebanon's Hizballah, the Taliban in Afghanistan, and Iraqi Shi'ite Muslim militant groups.
According to a statistical annex prepared by the U.S. National Counterterrorism Center, there were more than 11,500 terrorist attacks in 72 countries last year. These caused more than 13,200 deaths, with more than 75 percent of them occurring in South Asia and the Middle East, Radio Free Europe reports.