"What we are going on is the commitment that Chairman Kim (Jong Un) made to our president, and that is the commitment to denuclearize. That is something that we certainly anticipate that he will hold up his end of the bargain," State Department spokeswoman Heather Nauert told reporters on Tuesday.
The comments come on the heels of a Washington Post report that cited U.S. intelligence officials claiming North Korea has yet to stop producing new ballistic missiles. The report also showed satellite imagery suggesting Pyongyang was continuing to develop develop intercontinental ballistic missiles despite Kim's commitment to Trump in Singapore.
Arms control experts confirmed to NBC News that both satellite photos and U.S. intelligence assessments show that the rogue regime is sprinting to add more missiles to its budding arsenal. The State Department and the Pentagon declined to comment on the intelligence assessments regarding North Korea's missile program.
The Washington Post report comes less than two months after Trump tweeted that North Korea no long posed a nuclear threat.
"There is no longer a Nuclear Threat from North Korea. Meeting with Kim Jong Un was an interesting and very positive experience. North Korea has great potential for the future!," Trump wrote a day after meeting with Kim in Singapore.
Secretary of State Mike Pompeo acknowledged in Senate testimony last week that North Korea is still making fissile material that is used in making nuclear weapons.
"Yes, they [North Korea] continue to produce fissile material, yes," he said, adding that he could not elaborate further on the matter publicly due to the sensitive nature of the matter.
Meanwhile, the top U.S. military commander on the Korean Peninsula said in July that the material needed for North Korea to make nuclear bombs is still intact, even after the historic summit in Singapore aimed at denuclearizing Pyongyang.
North Korea's nuclear "production capability is still intact," Army Gen. Vincent Brooks, the commander of U.S. forces in South Korea, told the recent Aspen Security Forum via teleconference. "We haven't seen a complete shutdown of production yet. We have not seen a removal of fuel rods."
Under Kim, the reclusive state has conducted its most powerful nuclear test, launched its first-ever intercontinental ballistic missile, and threatened to send missiles into the waters near Guam.
Since 2011, North Korea has fired more than 85 missiles and conducted four nuclear weapons tests — which is more than what his father, Kim Jong Il, and grandfather, Kim Il Sung, launched over a period of 27 years.
North Korea remains the only nation to have tested nuclear weapons this century.