WASHINGTON -- An unpredictable North Korea, with its nuclear weapons and missile programs, stands as a serious threat to the United States and East Asia nations, the director of National Intelligence warned Tuesday in a sobre assessment of worldwide threats.

Testifying before a Senate panel, James R. Clapper delivered the U.S. intelligence community's overview of global threats posed by terrorism, cyber attacks, weapons of mass destruction, the months-long civil war in Syria and the unsettled situation in post-Arab Spring nations.

The outlook on North Korea comes as the communist regime announced that it was "completely scrapping" the 1953 armistice that ended the Korean War and has maintained peace on the peninsula for more than half a century. The Obama administration on Monday slapped new sanctions against North Korea's primary exchange bank and several senior government officials as it expressed concern about the North's "bellicose rhetoric."

"The Intelligence community has long assessed that, in Pyongyang's view, its nuclear capabilities are intended for deterrence, international prestige and coercive diplomacy. We do not know Pyongyang's nuclear doctrine or employment concepts," Clapper told the Senate Intelligence Committee. "Although we assess with low confidence that the North would only attempt to use nuclear weapons against U.S. forces or allies to preserve the Kim regime, we do not know what would constitute, from the North's perspective, crossing that threshold."

North Korea, led by its young leader Kim Jong Un, has defied the international community in the last three months, testing an intercontinental ballistic missile and a third nuclear bomb.

Pressed on North Korea, Clapper said he was "very concerned about the actions of the new young leader." He described the talk emanating from Pyongyang as "very belligerent."

"The rhetoric, while propaganda-laced, is an indicator of their attitude," Clapper said.

Testifying before the Senate Armed Services Committee, the general in charge of U.S. Strategic Command said he is "satisfied" that existing U.S. missile defences can defend against a limited attack from North Korea.

Air Force Gen. Robert Kehler also said he is confident the country is adequately defended from a limited attack by Iran, "although we are not in the most optimum posture to do that today."

In Syria, President Bashar Assad's inability to quash the uprising in his country increases the possibility that he will use chemical weapons against his people, Clapper said.

"We assess that an increasingly beleaguered regime, having found its escalation of violence through conventional means inadequate, might be prepared to use chemical weapons against the Syrian people," he said. "In addition, groups or individuals in Syria could gain access to chemical weapons-related material."

Sen. Dianne Feinstein, a Democrat and chairwoman of the Senate Intelligence committee, described Syria as a "massive and still growing humanitarian disaster under way with no end in sight."

The United Nations estimates more than 70,000 people have been killed in the civil war, which started two years ago against Assad's rule.

Clapper warned about the impact of automatic, across-the-board budget cuts that kicked in March 1, arguing that it will degrade the ability of the intelligence community.

The top U.S. intelligence chief said the budget cuts have jeopardized America's security and safety -- and will only get worse over time. He said the reductions will shave about $4 billion from intelligence budgets. He said that amounted to about 10 per cent of national intelligence programs.

Clapper said if the government is not careful, "we risk another damaging downward spiral."

The report said North Korea has exported ballistic missiles and associated materials to a number of countries, including Iran and Syria. It also displayed what appeared to be a road-mobile intercontinental ballistic missile and put a satellite in orbit with a launch vehicle.

"These programs demonstrate North Korea's commitment to develop long-range missile technology that could pose a direct threat to the United States, and its efforts to produce and market ballistic missiles raise broader regional and global security concerns," the report said.

Clapper testified with newly installed CIA Director John Brennan and FBI Director Robert Mueller. Feinstein pointed to successes in the battling terrorism -- 105 terrorism-related arrests in the United States in the past four year and 438 convictions since Sept. 11, 2001.

In assessing Iran, the report stated flatly that Tehran is developing nuclear capabilities to enhance its security and influence and "give it the ability to develop a nuclear weapon." But the report stopped short of saying a decision has been made.

"We do not know if Iran will eventually decide to build nuclear weapons," the report said.

Clapper explained that in the last year, Iran has made progress in working toward producing weapons-grade uranium. However, the report said Iran "could not divert safeguarded material and produce a weapon-worth of weapons-grade uranium before this activity is discovered."

The assessment on Iran comes shortly before President Barack Obama's trip to Israel, where Prime Minister Benjamin Netanyahu has warned that the world has until this summer -- at the latest -- to keep Tehran from building a bomb. The Israeli leader repeatedly has indicated Israel is willing to strike militarily to stop Iran, a step that would likely drag in the United States.

The report said terrorist threats are in transition with an increasingly decentralized global jihadist movement. The Arab Spring, however, has created a spike in threats to U.S. interests in the region "that likely will endure until political upheaval stabilizes and security forces regain their capabilities."

Associated Press writer Richard Lardner contributed to this report.