WASHINGTON — At the start of Donald Trump’s presidency, American intelligence agencies told the new administration that while North Korea had built the bomb, there was still ample time — upward of four years — to slow or stop its development of a missile capable of hitting an American city with a nuclear warhead.
The North’s young leader, Kim Jong-un, faced a range of troubles, they assured the new administration, giving Mr. Trump time to explore negotiations or pursue countermeasures. One official who participated in the early policy reviews said estimates suggested Mr. Kim would be unable to strike the continental United States until 2020, perhaps even 2022.