(2nd LD) S. Korea, U.S. in talks on using secondary boycott as option to rein in N. Korea
(ATTN: ADDS more comments in last 2 paras)
SEOUL, July 10 (Yonhap) -- Talks are underway between South Korea and the United States on possibly using a "secondary boycott" aimed at toughening sanctions against North Korea's evolving missile and nuclear