The White House on Monday dismissed North Korea’s insistence that a senior State Department official whom Pyongyang called ‘‘rude human scum’’ be barred from upcoming nuclear talks, in an exchange that underscored the obstacles facing the halting diplomatic effort.White House Press Secretary Scott McClellan defended Undersecretary of State John R. Bolton — called a ‘‘bloodsucker’’ by N Korea — and said President Bush would decide who would speak for the US at the meeting on nuke programme. In calling North Korean leader Kim Jong Il a ‘‘tyrannical rogue’’ and life in the Stalinist state a ‘‘hellish nightmare,’’ Bolton was ‘‘speaking for the administration,’’ McClellan said. Pyongyang’s KCNA fired back on Saturday, declaring that in light of Bolton’s ‘‘political vulgarity and psychopathological condition.we have decided not to consider him as a US administration official any longer.’’ (LAT-WP)