WASHINGTON—The United States said on Saturday that documents handed over by North Korea detailed its weapons-grade plutonium program as far back as 1986 and were an "important first step" in getting a full declaration of the North's nuclear activities.
In a "fact sheet" providing limited details of the documents, the State Department said the 18,000 pages covered some three major periods when plutonium was produced by North Korea for nuclear weapons.
"The United States and the other parties continue to press the DPRK to fulfill its declaration commitment," said the statement, referring to Pyongyang's failure to produce a full declaration of its nuclear activities by the end of last year.
The documents were given by Pyongyang to the State Department's Korea expert, Sung Kim, on Thursday who then hand-carried them over the heavily fortified demilitarized zone into South Korea on Saturday.
Kim spoke briefly and said officials now needed to investigate the contents of the documents. The State Department said seven large boxes were carried across the border.
He will return to Washington on Monday where the State Department said the documents would be "examined thoroughly" by a U.S. nuclear verification team and other experts.
Under a six-country deal, North Korea was required to provide a full accounting of its fissile material and nuclear weaponry as well as answer U.S. suspicions that it enriched uranium for weapons and proliferated technology to Syria.
If North Korea makes the declaration, the United States has promised to take it off its terrorism blacklist and remove sanctions that restrict Pyongyang from tapping into international finance.
"These operating records date back to 1986 and are expected to cover reactor operations and all three reprocessing campaigns undertaken by North Korea," the State Department said of the plutonium logs.
"Review of the operating records provided on May 8 will be an important first step in the process of verifying that North Korea's declaration is complete and correct," it added.
North Korea, which tested a nuclear device in October 2006, is thought by Washington to have produced about 110 lbs (50 kg) of plutonium, which proliferation experts said is enough for about eight nuclear bombs.
The documents consist of the operating records of the Yongbyon nuclear complex where North Korea has produced its stock of weapons-grade plutonium until it was shut down in July last year under a deal with the United States, Japan, the two Koreas, China and Russia
Since November, U.S. experts have been on the ground at Yongbyon overseeing disablement of the reactor and the State Department said eight out of 11 agreed disablement activities at three core facilities on the complex had been completed.
As of mid-May, more than one-third of spent fuel rods had been discharged, the State Department added.
The main sticking point in the declaration has been Pyongyang's reluctance to discuss any transfer of nuclear technology to other countries, notably Syria, as well as its suspected pursuit of uranium enrichment.
U.S. President George W. Bush said in late April he released intelligence about the suspected North Korea-Syria nuclear collusion to put pressure on Pyongyang to come clean on all its nuclear activities.
Pyongyang has yet to respond to White House charges that North Korea was helping Syria build the reactor that could produce arms-grade plutonium.
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