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President Trump and Kim Jong Un will sign an agreement to acknowledge the progress of the talks and pledge to keep momentum going, a US official told CNN.

The official said he would not get ahead of the President on hard specifics of any agreement.

Trump surprised reporters by announcing there would be "a signing" in the afternoon, during a stroll around the Capella Hotel with Kim.

No official events had been planned until Trump's meeting with the press at 4 p.m. local time (4 a.m. ET).