Washington has learned that North Korea imported large amounts of high-intensity aluminum pipes from Russia in 2002, a finding feared to strain already-tense bilateral ties.

Japan’s Asahi Daily quoted officials with the six-party talks as saying the North purchased around 150 tons of such pipes, which could produce about 2,600 centrifuges for uranium enrichment.

The daily reported the Communist nation also imported 20 centrifuge prototypes and plans from Pakistan, a fact that was uncovered by U.S. intelligence in June 2002.

In October 2002, the U.S. government confronted the North on the centrifuge issue during high-level bilateral talks in Pyongyang. The North subsequently admitted to its uranium enrichment plans, triggering the collapse of the 1994 Geneva Framework Agreement and the second nuclear crisis.