The U.S. National Director of Intelligence says the al-Qaida terrorist network remains the top concern of the intelligence community, followed closely by the nuclear activities of Iran and North Korea.

In a rare public session of the Senate Intelligence Committee, National Intelligence Director John Negroponte said there has been much progress in fighting global terrorism.

He said U.S.-led counterterrorism efforts last year continued to disrupt al-Qaida's operations and take out its leaders. But he says the terrorist network remains the top threat of the United States.

"The organization's core elements still plot and make preparations for terrorist strikes against the homeland and other targets from bases in Pakistan-Afghanistan border areas," he said.

Negroponte said al-Qaida would continue to seek to acquire chemical, biological and nuclear weapons to use against the United States.

In his first public testimony before Congress since his confirmation hearings last April, Negroponte said the intelligence community is also concerned about Iran.

"We judge that Tehran probably does not have a nuclear weapon and probably has not yet produced or acquired the necessary fissile material," he added.  "Nevertheless, the danger that it will acquire a nuclear weapon and the ability to integrate it with ballistic missiles that Iran already possesses is reason for immediate concern."

Negroponte's comments come as the International Atomic Energy Agency (IAEA) is considering whether to report Iran to the U.N. Security Council over its nuclear program.  Tehran says its nuclear activities are for peaceful purposes, but has threatened to begin full-scale nuclear enrichment activities and halt cooperation with the IAEA if it is reported to the council.

On North Korea, Negroponte told the Senate committee that Pyongyang's claims that it has nuclear weapons is "probably true."

"Pyongyang sees nuclear weapons as the best way to deter superior United States and South Korean forces, to ensure regime security, as a lever for economic gain and as a source of prestige," he explained.

As envoys from six nations work to restart talks aimed at ending North Korea's nuclear program, Negroponte said the country remains a major challenge to global nonproliferation efforts.

He said the United States sees no evidence of organized opposition among North Korea's political or military elite to the regime of Kim Jong Il.

The National Intelligence Director also spoke about Iraq, saying Sunni disaffection with the emerging government is what he called the "primary enabler" of the insurgency there.  He cautioned that even if a broad inclusive national government emerges, there likely will be a lag time before there is a dampening effect on the insurgency.  He added that insurgents' use of improvised explosive devices remains a significant threat to coalition forces and a complex challenge to the intelligence community.

Responding to the recent Palestinian elections, Negroponte said Hamas' victory does not necessarily mean the search for peace between Israel and the Palestinians is halted irrevocably.

Negroponte praised Saudi Arabia and Pakistan as key allies in the war on terrorism.  

But he expressed concern that private Saudi citizens continue to contribute money to charities linked to terrorist groups.   And he said Pakistan's President, General Pervez Musharraf, has made only limited progress moving his country to democracy.

Negroponte offered a warning about another U.S. ally in the fight against terrorism, Russia.

"President Putin's drive to centralize power and assert control over civil society, growing state control over strategic sectors of the economy and the persistence of widespread corruption raise questions about the country's direction," he said.  "Russia could become a more inward-looking and difficult interlocutor for the United States over the next several years."

The intelligence official said Central Asia remains plagued by political stagnation and repression, rampant corruption and widespread poverty and widening socio-economic equalities and other problems that nurture nascent radical sentiment and terrorism. 

"In the worst, but not implausible case, central authority in one or more of these states could evaporate as rival clans or regions vie for power, opening the door to an expansion of terrorist and criminal activity on the model of failed states like Somalia, and when it was under Taleban rule, Afghanistan," he explained.

Negroponte expressed concern about China's repression of domestic opposition.

"Beijings determination to repress real or perceived challenges from dispossessed peasants to religious organizations could lead to serious instability at home and less effective policies abroad," he said.

Negroponte also said an effort by Nigeria's President Olusegun Obasanjo to change the constitution and seek a third term could unleash major turmoil and conflict, leading to a disruption of the country's oil supply, secessionist moves by regional governments, major refugee flows and instability elsewhere in Africa.

He also said he expects Venezuela's President Hugo Chavez to deepen his ties with Cuban leader Fidel Castro, and seek closer economic, military and diplomatic ties with Iran and North Korea.