President Donald Trump says a Singapore summit planned for June 12 with North Korea's Kim Jong Un "may not work out."
Trump is meeting with South Korean President Moon Jae-in on Tuesday at the White House for consultations ahead of the planned summit with Kim.
But the president has already suggested that the summit may be delayed.
North Korea pulled out of planned peace talks with South Korea last week, objecting to long-scheduled joint military exercises between the U.S. and the Republic of Korea forces.
North Korea has also threatened to abandon the planned Trump-Kim meeting over the U.S. insistence on denuclearizing the Korean Peninsula.