US President Donald Trump did not ruled out the possibility of cancelling the meeting with North Korea's leader Kim Jong-un, Independent reported.
Kim Jong-un would be making a "great mistake" if he believed he could "play" Donald Trump when they meet next month, Mike Pence, the US vice president, has warned.
When he was asked if Mr Trump could still walk away from the summit, scheduled for 12 June in Singapore, he replied: "Well there's no question."
Trump is to meet South Korea's president, Moon Jae-in, on Tuesday, three weeks before his scheduled meeting with Kim Jong-un.
Mr Moon's visit to the White House was originally planned to fine-tune a joint strategy for dealing with the North Korean leader, but it has now instead become more of a crisis session after North Korea threatened to pull out of the summit.