North Korea is preparing for a massive military parade to mark the 75th anniversary of its ruling party next month.
Foreign experts say past North Korean underwater-launched missile tests were conducted from a submersible barge.
U.S. Forces Korea Gen. Robert Abrams said the command is looking for other options.
The account comes from CNN's review of Bob Woodward's upcoming book, "Rage."
Some experts say Pyongyang will likely avoid serious talks with Washington before the U.S. presidential elections.
Trump and Kim have met three times since embarking on high-stakes nuclear diplomacy in 2018.
North Korea has previously demanded the U.S. lift international sanctions and provide security guarantee.
Trump and North Korean leader Kim Jong Un have met three times since embarking on their high-stakes nuclear diplomacy.
President Trump has met three times with North Korean dictator Kim Jong Un during his presidency.
The last significant contact between the two sides was outside of Stockholm last October.
The campaign of President Donald Trump released a letter from 235 retired senior officers backing his re-election.
The news comes four years after the Air Force laid out initial plans for what its future fighter jets might look like.
The recent exercises were one of many the Air Force is conducting to test its Advanced Battle Management System.
A veteran of the Marine Corps and Army National Guard, he went through boot camp more than four decades ago.
Cmdr. Robert Arias is at least the third Navy commander removed from his job in recent weeks.