International efforts to prevent a threatened North Korean nuclear test intensified, with South Korea stepping up diplomatic overtures, Japan seeking censure by the UN and Russia pledging to do "everything so that doesn't happen." North Korea's neighbors closed ranks as a pro-North newspaper warned Thursday that the isolated regime wasn't bluffing when it announced Tuesday that it would conduct a nuclear test to prove it is a nuclear power. Attention nevertheless focused on whether the threat was real or merely saber-rattling intended to gain concessions in long-stalled negotiations on its nuclear program, and when a test, if any, might come.