He said the documents on a weapons-grade plutonium programme dating back to 1986 appear to be "a complete set" and required translation, adding that a full review would take several weeks.
"I do think these documents are an important first step in terms of verifying North Korea's declaration," he said at a press conference in Washington on Tuesday.
But he added: "Obviously, the documents themselves alone are not enough."
|"We do expect the declaration package to address all of our concerns"|
Sung Kim, state department North Korea expert
Kim said a full declaration - part of 11 steps North Korea must take to dismantle its nuclear reactor – remains a US requirement.
"I don't believe they consider this to be the declaration itself," he said, adding that the papers were "important supporting documents for the declaration".
"I think they will be submitting a separate document to the Chinese that would be their declaration.
"We do expect the declaration package to address all of our concerns including any activities they might have had with uranium enrichment and any sort of co-operation with foreign countries," he said.
The records are a key element in the six-party effort to get North Korea to abandon its nuclear weapons programme.
The documents submitted so far include daily and operational logs, books, records of receipts and operational records.
North Korea has said that it will fully co-operate with the US on verifying its nuclear declaration and has agreed to provide documents and other records for other facilities during the verification phase.
The Bush administration hopes the documents will help convince sceptics in congress and elsewhere that a nuclear disarmament deal with the North is still worth having, despite delays, foot-dragging and revelations about the alleged sale of North Korean nuclear technology to Syria.
Tuesday's press conference came as US legislators pushed for a bill to require George Bush, the president, to certify that North Korea is not transferring nuclear technology to Iran and Syria before Pyongyang receives its coveted goal of being taken off a US "terrorism blacklist".
The measure, which was considered on Tuesday by the US House of Representatives, could hinder the Bush administration's push to settle a nuclear disarmament deal with the North, but a vote on the measure was postponed.
Under the legislation, Bush would also have to certify that North Korea has provided a "complete and correct" and verifiable declaration of all its nuclear programmes before removing it from the blacklist.
A full declaration by the North has been held up partly due to Pyongyang's reluctance to discuss any transfer of nuclear technology to other countries such as Syria, and to account for its suspected pursuit of uranium enrichment.
The US accuses North Korea of helping Syria with a suspected nuclear reactor project, a claim Pyongyang denies.
It also says the North was pursuing a uranium enrichment programme which could provide it with a second way to produce fissile material for nuclear weapons in addition to the plutonium-based programme used in its 2006 nuclear test.