* Attacks drop in Iraq in 2009
* Al Qaeda "adaptable" -- still wants to attack U.S.
* Yemen and Pakistan countries of biggest concern (Updates with quotes)
By Paul Eckert and Emma Ashburn
WASHINGTON, Aug 5 (Reuters) - Al Qaeda's core leadership in Pakistan remains the most formidable terrorist threat to the U.S. homeland and its growing presence across Africa challenges many states, the U.S. State Department said on Thursday.
Counter terrorism officials identified Pakistan and Yemen as the countries of greatest concern and said al Qaeda showed last year that it had growing ability to recruit citizens of the United States and Europe to fight for its militant cause.
Terrorist attacks worldwide and their death toll in 2009 were at their lowest in some four years, the State Department's annual "Country Reports on Terrorism" report said.
Terrorists carried out 10,999 attacks worldwide in 2009, the lowest number in five years, down from a recent high of 14,443 in 2006. The report said 14,971 people died in these attacks, down from recent high of 22,736 in 2006.
Al Qaeda, the group behind the Sept. 11 attacks, "has proven to be an adaptable and resilient terrorist group whose desire to attack the United States and U.S. interests abroad remains strong," it said.
The Taliban-led insurgency that U.S. troops are fighting in Afghanistan got funding and training from Al Qaeda and "remained resilient in the south and east and expanded its presence into the north and west."
ATTACKS IN PAKISTAN MUSHROOM
Afghanistan's troubles have increasingly spilled over into neighboring U.S. ally Pakistan.
"For the first time, Pakistan slightly surpassed Iraq in terms of large scale attacks - that is, attacks in which more than 10 people were killed. It also surpassed Iraq in terms of number of suicide bombings," said Russ Travers, deputy director of the National Counterterrorism Center.
Travers told reporters Pakistan's Northwest Frontier province went from 16 attacks in 2005 to 940 last year.
Yemen's security situation deteriorated during 2009, with the merger of the Yemeni and Saudi branches of al Qaeda to form al Qaeda in the Arabian Peninsula (AQAP), it said.
The threat was driven home with the December 25 suicide bombing attempt on a flight into Detroit by Nigerian citizen Umar Farouk Abdulmutallab, who admitted to having been trained in Yemen.
"Yemen is grappling with serious poverty and is the poorest country in the Arab world," said Daniel Benjamin, State Department Coordinator for Counterterrorism.
"The lack of resources inhibits good governance, the delivery of services, and the effectiveness of the security provision that is needed to deal with terrorism," he told a news briefing.
US CITIZENS JOIN VIOLENCE
American citizens are not immune to the call of al Qaeda, Benjamin said.
"Not only have there been more cases of Americans becoming operatives for foreign terrorist organizations, we have also seen U.S. citizens rise in prominence as proponents of violent extremism," said the report. It identified AQAP's Anwar al-Aulaqi as "an influential voice of Islamist radicalism among English-speaking extremists."
The report to Congress -- published here -- also highlighted concerns about al Qaeda inroads across Africa, from the Maghreb states in the northwest to Somalia, which it called "highly unstable, and a permissive environment for terrorist transit and training."
The State Department said Iraq in 2009 saw a sharp reduction in the number of security incidents, and a decrease in civilian casualties, enemy attacks, and improvised explosive devices attacks.
Iran, one of four countries designated state sponsors of terrorism, provided backing for extremists in its region that "had a direct impact on international efforts to promote peace, threatened economic stability in the Gulf, jeopardized the tenuous peace in southern Lebanon, and undermined the growth of democracy," the State Department said. (Reporting by Emma Ashburn and Paul Eckert; editing by Vicki Allen and Alan Elsner)