Trump has received another letter from Kim, which Sanders described on Monday as "very warm" and "very positive", noting that the White House ' title=' White House '>White House will not release the letter unless Kim agrees, reports CNN.

The primary intent of the letter, she said at Monday's briefing, was to "request and look to schedule another meeting" between the two leaders, something the White House ' title=' White House '>White House is "open to".

She said that the White House ' title=' White House '>White House is "already in the process of coordinating" another meeting, but declined to provide further details on a time or location.

Sanders cited the letter as "further evidence of progress" toward denuclearization, noting that the latest parade was "not about their nuclear arsenal".

The letter, she said, showed a "commitment to continuing conversations".

Sanders' comments came hours after Bolton said Trump has "tried to hold the door open" for Kim to denuclearize, but the US is still waiting on Pyongyang to take those steps, CNN said.

South Korean officials also said last week that Kim has "unwavering trust for President Trump" and wants to achieve the denuclearization of the Korean Peninsula before the US leader finishes his term.