(CNN) A senior State Department official on Thursday expressed optimism that the denuclearization of North Korea could be achieved during President Donald Trump's first term, despite the lack of progress during the recent Hanoi summit and expert assertions to the contrary.

"We still believe that this is all achievable within the President's first term, and that's the timetable we're working on," the official said. "We have discussed extensively the outlines of the calendar that allow us to do that, and it is doable."

The official said they "are pushing very hard with our North Korean interlocutors" their goal of denuclearization within the first term.

"The ultimate driver to this is not going to be the amount of days it takes, it's going to be the degree to which we can satisfactorily achieve the steps which we feel are necessary to the final, fully verified denuclearization of North Korea," they said.

The official's statements come in the wake of a failed summit last month between Trump and North Korean leader Kim Jong Un. The meeting failed to make any progress toward the US' goal, resulting instead in what Trump has come to call "the walk." The official maintained Thursday that both sides left "on very good terms" but conceded that "we're not as far along as we'd like to be."

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