World leaders expressed concern on Thursday that North Korea will quit six-party nuclear disarmament talks and will  bolster its nuclear weapons arsenal.
North Korea causes other countries to worry
( z1 cause :ARG0 ( z2 country :name ( z3 name :op "North" :op "Korea" ) ) :ARG1 ( z4 worry :ARG0 ( z5 country :mod ( z6 other ) ) ) )