They 're only going to further isolate the North Koreans and undermine international efforts to bring peace and stability to northeast Asia , '' Earnest said . NEW : South Korean troops enter industrial zone despite construction of lines . NE : The North clears them to cross the border through another line , Yonhap says . U.S. intelligence official expresses concern about ` ` ratcheting up of rhetoric '' The announcement follows a slew of recent statements from North Korea .
NEW : South Korean troops enter industrial zone despite construction of lines . NE : The North clears them to cross the border through another line , Yonhap says . U.S. intelligence official expresses concern about ` ` ratcheting up of rhetoric '' The announcement follows a slew of recent statements from North Korea .