North Korea is technically capable of building a long-range missile that can hit the United States despite a test failure last year, a senior US military intelligence official said Tuesday.

Lieutenant General Michael Maples, director of the Defense Intelligence Agency, said North Korea has probably learned from the failure of its Taepodong-2 missile during a test in July, and made changes to its other missiles.

"I believe they have the technical capability, as we saw by the Taepodong, but they have not successfully tested it yet," he told the Senate Armed Services Committee.

Asked how long before North Korea would have a missile capable of reaching the United States, he said, "I would probably estimate it's not a matter of years."

Maples made the comments in testimony about global threats that singled out North Korea and Iran as the two states of greatest concern.

In the case of North Korea it cited proliferation fears heightened by the July missile tests and North Korea's nuclear test in October.

North Korea agreed on February 13 on steps toward disabling its nuclear program in return for US supplies of fuel oil or other economic assistance.

Michael McConnell, the national director of intelligence, said US intelligence was unable to monitor North Korea compliance with the agreement "at the level we would like."

"We can verify many of the conditions from external observation, but not at the level you're asking about in terms of detail," he said.

"There's some open questions, but so far the indications are in the positive direction," he said.

North Korea has a known nuclear reactor at Yongbyon but US intelligence also believes it was secretly pursuing a separate uranium enrichment program, which also would be covered by the agreement.

Another intelligence official, Joseph Detrani, said US intelligence had high confidence in 2002 that North Korea was acquiring equipment for a uranium enrichment program.

US intelligence still believes the program exists, but its confidence in that assessment is now "mid-level."