Al Qaeda poses the gravest terrorist threat to the United States and an emboldened Hezbollah is a growing danger, the U.S. intelligence chief said Thursday.

In his annual review of global threats, National Intelligence Director John Negroponte highlighted an increasingly worrisome assessment of Hezbollah — backed by Iran and Syria — since its 34-day war with Israel last year.

"As a result of last summer's hostilities, Hezbollah's self-confidence and hostility toward the United States as a supporter of Israel could cause the group to increase its contingency planning against United States interests," Negroponte told the Senate Intelligence Committee.

He depicted a more multifaceted terrorist threat than in years past. Since the attacks of Sept. 11, 2001, U.S. spy agencies have stressed the threat from Al Qaeda and associated Sunni extremist groups, rather than from Hezbollah and other Shiite Muslim groups.

Hezbollah has a global fundraising network, but has not directly attacked U.S. interests in years. It was responsible for the 1983 bombings of the U.S. Embassy and the Marine barracks in Beirut, Lebanon, that killed hundreds of American servicemen. The group's Saudi wing, in coordination with the larger Lebanese Hezbollah, is blamed for the Khobar Towers bombing in Saudi Arabia in 1996.

A separate report by government task force predicted that attacks against America and its allies probably would increase in the next few years because terrorists' intentions have not diminished and their methods are "very nimble and very complex."

The panel said Al Qaeda is a diminished organization overall with a core that is "resilient and in some respects resurgent," according to the chairman, former Rep. Lee Hamilton, D-Ind.

Negroponte said Iraq is at a "precarious juncture" and the Baghdad government needs to establish secular institutions that can bridge sectarian differences. The flow of weapons and fighters from Iran and Syria in support of Shiites must be stemmed, he said, and Al Qaeda in Iraq must be stopped.

The head of the Defense Intelligence Agency painted a picture of unchecked bloodshed in Iraq that has led more people to turn to sectarian groups for their basic needs and threatened the country's unity. Robust criminal networks are exacerbating the situation, Lt. Gen. Michael Maples said.

His agency believes the U.S.-led coalition in Iraq "is the primary counter to a breakdown in central authority," Maples said.

Al Qaeda is America's top concern among terrorist groups, he said. Osama bin Laden's network maintains active connections "that radiate outward from their leaders' secure hide-out in Pakistan to affiliates throughout the Middle East, northern Africa and Europe," Negroponte said.

Conventional explosives are the "most probable" means of attack from the group, he said, but there are reports Al Qaeda is trying to obtain chemical, biological, radiological and nuclear weapons.

In his written testimony, FBI Director Robert Mueller said Al Qaeda's choice of targets and methods most likely will focus on the aviation, energy and mass transit sectors. The group is interested, too, in attacks against large public gatherings and symbolic targets such as monuments.

Their testimony came as President Bush pursues a revised course in Iraq and overhauls his national security team. Last week, the president nominated Negroponte to the No. 2 State Department post and asked former National Security Agency Director Mike McConnell to succeed Negroponte.

Senate Democrats were skeptical that Bush's decision to send 20,000 more U.S. troops would improve security in Iraq.

The Senate committee chairman, Sen. Jay Rockefeller, said he was concerned that "misguided policies of the administration" have increased the threat to the United States. "I believe our actions in Iraq have placed our nation more at risk to terrorist attack than before the invasion," said Rockefeller, D-W.Va.

The committee's top Republican, Sen. Kit Bond of Missouri, said now that Bush's has detailed his plan, "It is time for the Iraqis to step up to the plate or we will obviously consider other options."

In his first hearing as chairman, Rockefeller took issue with counterterrorism programs undertaken by the Bush administration, including secret CIA prisons. He pledged to hold hearings and said the administration can "no longer stonewall" requests for information now that Democrats control Congress.

Outlining other global threats, the intelligence officials told senators:

— The DIA believes attacks in Afghanistan from the Taliban-led insurgency will increase this spring. "Nearly five years after the Taliban's fall, many Afghans expected the situation to be better by now and are beginning to blame President (Hamid) Karzai for the lack of greater progress," Maples said.

— In Somalia, where the Islamic government has collapsed, the transitional U.N.-backed government faces the same obstacles that have prevented political stability since 1991. "More turmoil could enable extremists to regain their footing. ... Al Qaeda remains determined to exploit turmoil in Somalia," Negroponte said.

— Iran and North Korea raise the greatest concerns regarding weapons proliferation. Iran, he said, "is determined to develop nuclear weapons — despite its international obligations and international pressure." He said the country "is continuing to pursue uranium enrichment and has shown more interest in protracting negotiations than reaching an acceptable diplomatic solution."

— The U.S. has identified 21 countries — Iran, North Korea and China are of highest concern — that can develop weapons of mass destruction or acquire sensitive weapons technologies, Mueller said. The FBI and other agencies have conducted joint investigations that have led to both arrests and intelligence.

The separate report by a task force of the Homeland Security Advisory Council said the most significant threat to the U.S. arises from the radicalization of Islam, particularly in underdeveloped societies.

The council, which advised the Homeland Security secretary, recommended that the government curb the Islamic radicalization of inmates in U.S. prisons; hire more people from different cultures and more people who speak more languages; and study attacks abroad and design domestic tactics to counter those methods.