The review report, made public this week, concluded that missile threats from several states, including Iran, Syria, China and Russia, are growing "quantitatively and qualitatively," and it outlined Pentagon plans for silo-based and mobile anti-missile systems to counter them.

On North Korea, the report disclosed for the first time the U.S. intelligence estimate of when Pyongyang will be able to reach the technically challenging threshold of producing a nuclear device small enough to be carried on a missile.

"We must assume that sooner or later, North Korea will have a successful test of its Taepodong-2 and, if there are no major changes in its national security strategy in the next decade, it will be able to mate a nuclear warhead to a proven delivery system," the report said.

U.S. intelligence officials said North Korea was one of at least three states — along with Libya and Iran — that benefited from the spread of nuclear technology provided by the network of suppliers headed by Pakistani technician A.Q. Khan. Included with that assistance and discovered when Libya gave up its Khan-supplied nuclear goods were Chinese-language documents on how to make a warhead for a missile, the officials have said.

U.S. intelligence agencies suspect but have not confirmed that North Korea also obtained the warhead-design documents from Mr. Khan.

North Korea's two underground nuclear tests and its development of long-range missiles is a major worry, the report said, noting that Iran also is developing long-range missiles.

Defense Secretary Robert M. Gates said in Senate testimony this week that the Pentagon is seeking $8.4 billion for missile defenses under what he described as a phased plan to shift the focus from larger ground-based long-range interceptors to shorter-range missile defenses, like the Navy's SM-3 ship-based missile interceptor.

"We have deployed ground-based interceptors at Fort Greely [in Alaska]. We have a very aggressive test program that has been successful. We believe that those interceptors give us the capability to deal with launches from either Iran or North Korea, a small-scale threat," Mr. Gates said.

Chuck Downs, a former Pentagon official and specialist on North Korea, said the North Korean drive for a long-range nuclear missile is part of Pyongyang's objective of being able to threaten the United States.

"They are a regime that has already relied on coercive threats, with their own people, with their neighbors and with the United States," he said.

Developing a nuclear-tipped Taepodong will be "the high point of their military development program," said Mr. Downs, head of the Committee for Human Rights in North Korea. "It should come as no surprise that they are seeking to develop this missile."

A defense official said the Defense Intelligence Agency told Congress last year that North Korea may be able to mate a nuclear warhead to a ballistic missile, noting that the Taepodong would be nuclear-capable. Additionally, DIA has stated that "North Korea could have several nuclear warheads capable of delivery by ballistic missiles."

"We have publicly stated that North Korea has a theoretical capability to produce a warhead and mate it with a missile, but we have no information to suggest they have done so," the official said.

Five years ago, Hillary Rodham Clinton, then a U.S. senator from New York, made headlines when she asked DIA director Vice Adm. Lowell Jacoby during a hearing whether North Korea had a nuclear warhead small enough to be carried on a missile. Adm. Jacoby said yes, but a Pentagon spokesman said later that officials did not know whether Pyongyang has a nuclear missile warhead capability.

The report said it was difficult to predict when the missile threat to the U.S. homeland will evolve, "but it is certain that it will do so."

Iran, meanwhile, announced Wednesday that it had conducted a rocket launch to place a satellite into orbit, a move that the White House called provocative.

North Korea's April 2009 Taepodong test failed to orbit a small communications satellites, but showed that Pyongyang has developed "many technologies associated with an [intercontinental ballistic missile (ICBM)]," the report said.

The missile-defense report outlines the Obama administration's plan for stepping up the deployment of short- and medium-range missile defenses, specifically to counter Iranian missiles.

"North Korea and Iran have shown contempt for international norms, pursued illicit weapons programs in defiance of the international community, and have been highly provocative in both their actions and statements," the report said. "They have exploited the capabilities available to them to threaten others."

Regional neighbors of both states may be limited in their actions and pursuit of interests because of the missile threat.

"Deterrence is a powerful tool, and the United States is seeking to strengthen deterrence against these new challenges," the report said. "But deterrence by threat of a strong offensive response may not be effective against these states in a time of political-military crisis. Risk-taking leaders may conclude that they can engage the United States in a confrontation if they can raise the stakes high enough by demonstrating the potential to do further harm with their missiles. Thus, U.S. missile defenses are critical to strengthening regional deterrence."

Iran has not stated its plan to build ICBMs, but the report said it continues to "pursue long-range ballistic missiles," including the Safir space launcher that was used in August 2008 and February 2009 to launch satellites.

Current U.S. missile-defense systems include 30 ground-based long-range interceptors in Alaska and California, ground-based mobile Patriot and Theater High-Altitude Area Defense (THAAD) systems and the Navy's SM-3 anti-missile interceptor, based on Aegis warships.

In the next several years, the Pentagon plans to develop and deploy several advanced variants of the SM-3 missile, including a ground-based version in Poland.

The report said the most advanced SM-3 will have some capability to knock out long-range missile warheads and will be ready for use in "the 2020 time frame."

The Obama administration canceled a plan to deploy long-range interceptors in Poland after Russia opposed the interceptor base and a related radar planned for the Czech Republic.

Instead, the administration will use ships deployed in waters closer to Iran to counter Iranian medium-range missiles, as well as interceptors in Poland to protect the Continent.

Critics of the scaled-back missile-defense plan say abandoning the proposal for stationing long-range missile interceptors in Europe will increase the U.S. vulnerability to a future Iranian missile strike on the United States.