"Eventually we are going to need a full declaration in order to complete a process of denuclearization. I expect that will come well before the end [of the denuclearization process]," the official told reporters during a briefing on the upcoming summit between President Donald Trump and North Korean Chairman Kim Jong-un.
According to the official, the United States is not discussing with North Korea the possibility of withdrawing its troops from the Korean Peninsula.
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"Withdrawing is not the subject of the discussion," the official told reporters during a press briefing.
The United States believes that North Korea can be fully denuclearized, the official added.
"The reason why we engage [in negotiations] is because we believe there is a possibility," the officials told reporters during a press briefing.
The situation on the Korean Peninsula has seen a significant improvement since last year after Kim boosted ties with South Korean President Moon Jae-in and held a historic summit with Trump in June.
The first US-North Korean summit in Singapore resulted in an agreement stipulating that Pyongyang would make efforts to promote the complete denuclearization of the peninsula in exchange for the United States and South Korea freezing their military drills.