North Korea handed over more than 18,000 pages of nuclear weapons documents to the a U.S diplomat visiting Pyongyang on Thursday that will help verify its plutonium holdings, senior U.S. officials said, according to Reuters. The officials said the documents were another step toward the goal of getting a full declaration of North Korea's nuclear activities, which has been delayed since the end of last year. The documents, between 18,000 and 19,000 pages, were handed over by the North Koreans to the State Department's Korea expert, Sung Kim, who is visiting Pyongyang, State Department spokesman Sean McCormack said. "He will bring back with him a significant number of documents relating to North Korea's plutonium program and we will have an opportunity over the coming days and weeks to assess the significance of these documents," McCormack said. Another senior U.S. official, who asked not to be named, said they provided detailed logs of how much plutonium was produced by North Korea. "This documentation consisting of thousands of pages will be essential to verifying North Korea's plutonium holdings," said the senior official.