WASHINGTON/SEOUL (Reuters) - North Korea has the ability to launch nuclear-armed ballistic missiles, although they would likely be unreliable, a Pentagon spy agency has concluded, as the United States and South Korea kept watch on Thursday for a missile test-launch by Pyongyang.
The Defence Intelligence Agency study, dated last month, appeared to be the first time the agency had reached such a conclusion.
"DIA assesses with moderate confidence the North currently has nuclear weapons capable of delivery by ballistic missiles, however the reliability will be low," said Republican U.S. Representative Doug Lamborn, who disclosed the conclusion during a congressional hearing on Thursday.
Lamborn said the agency reached the conclusion in a mostly classified March 2013 report. He did not say what range the nuclear-capable North Korean missiles might have.
General Martin Dempsey, chairman of the U.S. Joint Chiefs of Staff, declined to comment when asked if he agreed with that assessment, saying he had not seen the report.
The strong consensus inside the U.S. government is that North Korea does not yet have a nuclear device that would fit longer-range missiles which conceivably could reach U.S. territories.
Despite recent threats to attack U.S. bases and the South, North Korea started to welcome a stream of visitors for Monday's celebrations marking the birthday of its founder Kim Il-sung.
U.S. President Barack Obama said the United States would work diplomatically to reduce tensions with North Korea, while warning that Washington would take "all necessary steps" to protect America and its allies.
Obama met at the White House on Thursday with U.N. Secretary-General Ban Ki-moon, who called for China and other nations with influence over North Korea to help calm the situation.
North Korea has stationed as many as five medium-range missiles on its east coast, according to defence assessments by Washington and Seoul, possibly in readiness for a test-launch that would demonstrate its ability to hit U.S. bases on Guam.
"There are signs the North could fire off Musudan missiles any time soon," an unnamed intelligence source in Seoul told Yonhap news agency.
Most observers say Pyongyang has no intention of starting a war that would likely bring its own destruction, but they warn of the risks of miscalculation on the highly militarised Korean peninsula.
(Additional reporting by Jack Kim and Daum Kim in SEOUL, Sui-Lee Wee in BEIJING, John Ruwitch in SHANGHAI, and Patricia Zengerle, Mark Hosenball and Jeff Mason in Washington; Writing by Peter Cooney, Editing by Jim Loney)