Transcript for Defense chief: US poised to resume military exercises with S. Korea

We traveled to Singapore that historic summit between president trumpnd north Korean after Y rember the presiddeclaringhere is no longer a nuclear threat from H Korea. But tonight, what's happened? The new slsing from the ambasr to the U.N. Haley tonight saying north korayhave, quote, changed their min on denuclearization. Prest trump at ly canceling Mike pomp Newes trip. And what defenec Mattis is now warning tot. Here's ABC's chiefte correspondent Jonathan Karl tonight. Repthe clearest sign yett president trum dream of a grand nuclear deal with north koray be fadi away, U.N. Ambassador I Haley today said Jong-un may not want to give up Pons afterall. Lk, are they wishing or maybe aging their minds on denuclea it's possible. Reporter:n Singapore, the made it sound like an almost done deal. Mr. President, hegree to denuclearize? We'tathat price very very, ry quickly absolutely. Reporter: As soon as he returned to Washington, he cleared "T is no longer a nur threat fm north Korea." From Kim trump at the use shortly bef T Singapore summit, prompted the presidentall off the next round of talks. President canceled secretary oftate Pompeo'sp to Ng, E are not making sufficient progress with respect the denuclearization." Shortly after that, sounds of fury out of North Korea. Stcusing thenited of "Double-dealing" and "Hatching final plot to a war" to "Commit serves merciless punishment." And in a signifi development, defense secretary defen Jim Mattis today south Korea. We at this ti to suspeny more excises. Bit of whiplash on this, Jon Karl. 'S at the white house tonight. Jon, the esident, course, declared the nuclear threat was over. Wet heard fm the cr there signaling that cases could resume. But the adminision tonig still hding out hope that tal somehow get back on track? Reporter: Well, the state department said today theto gage, but only when nokorea stands ready to T pse of getting of theirnukes. And David, even ahesi eo's tri to North Korea, heated his warm R to Kim Jong-un and said, quote, I look frd to seeing him so All right, Jon Karl on a tuesnight. Thyou, Jon. Next tonight, to Puerto Rico. And the

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