U.S. President Donald signaled an openness to talks with North Korea on Tuesday, citing "possible progress" after the regime told visiting South Korean envoys that it was prepared to halt tests of nuclear weapons and missiles and would put scrapping its atomic arsenal on the table for discussion — an apparent breakthrough after months of bellicose threats from both Washington and Pyongyang raised the specter of a devastating and bloody war.

The stunning diplomatic opening, unthinkable just months ago, presents the United States with both an opportunity and a challenge as Washington and its allies seek to resolve the long-festering nuclear issue, analysts as well as current and former U.S. officials said.

Trump said the North Korean steps toward U.S. demands that Pyongyang demonstrate a commitment to denuclearization "have been very positive."