U.S. Cites Signs of Korean Steps to Nuclear Test By DAVID E. SANGER and WILLIAM J. BROAD WASHINGTON, May 5 - White House and Pentagon officials are closely monitoring a recent stream of satellite photographs of North Korea that appear to show rapid, extensive preparations for a nuclear weapons test, including the construction of a reviewing stand, presumably for dignitaries, according to American and foreign officials who have been briefed on the imagery. North Korea has never tested a nuclear weapon. Bush administration officials, when asked Thursday about the burst of activity at a suspected test site in the northeastern...