North Korea slammed the U.S. on Saturday, claiming it had been "deceived" by Washington after 18 months of nuclear negotiations.

"We have been deceived by the US, being caught in the dialogue with it for over one year and a half, and that was the lost time for us,” Kim Kye Gwan, a top adviser to North Korea leader Kim Jong Un, said in a statement published by state media.

The last time North Korean and U.S. negotiators met was in early October but diplomatic talks fell through on the first day of meetings. President Trump and Kim previously met in Vietnam in February and Singapore in June 2018 but failed to reach a deal.

"Although Chairman Kim Jong Un has a good personal feelings about President Trump, they are, in the true sense of the word, 'personal'," Kim Kye Gwan added. "There will never be such negotiations as that in Vietnam, in which we proposed exchanging a core nuclear facility of the country for the lift of some UN sanctions in a bid to lessen the sufferings of the peaceable people even a bit."

Trump and Kim have had a friendly relationship, sending cordial letters to one another. North Korea said Saturday that Kim received birthday greetings from Trump but that it would not be enough to restart negotiations.

“The reopening of dialogue between the DPRK and the U.S. may be possible only under the condition of the latter’s absolute agreement on the issues raised by the former, but we know well that the U.S. is neither ready nor able to do so,” Kim Kye Gwan said, using the official name for North Korea, the Democratic People’s Republic of Korea (DPRK).

North Korea wants the U.S. to remove sanctions that are targeting its economy. Pyongyang has also been irritated by planned U.S.-South Korea military exercises, which the U.S. postponed in November.

North Korea had promised a “Christmas gift” for the U.S. this past holiday season, which some analysts believed to be an intercontinental ballistic missile test (ICBM). North Korea did not conduct any aggressive military exercises during that time.

The U.S. would like for North Korea to pursue a path to denuclearization as part of any future nuclear deal. Former National Security Adviser John Bolton has stated that the North Koreans would likely never give up their nuclear arsenal.