China has reportedly indicated to the United States that it will not block the referral of North Korea's nuclear issue to the U-N Security Council if the North conducts a nuclear test.

Japan's Nihon Keizai Shimbun quoted sources as saying on Wednesday that Beijing had hinted to Washington that if Pyongyang carries out a nuclear test, it would consider it a "serious problem" and a significant change in the situation.

According to the paper, China apparently delivered its stance in discussions with Assistant Secretary of State Christopher Hill, the top U.S. negotiator to the six-party talks, and in a telephone conversation between Secretary of State Condoleezza Rice and her Chinese counterpart, Li Zhaoxing, last week.