US Secretary of State Mike Pompeo said he is confident that North Korea fully understands the scope of the American desire for complete denuclearisation.
Pompeo's statement comes as the two countries negotiate after President Donald Trump's historic summit this month with North Korean leader Kim Jong Un.
"We've been pretty unambiguous in our conversations about what we mean when we say complete denuclearisation," Pompeo told a US Senate subcommittee hearing on Wednesday.
Trump has drawn some criticism from national security analysts for an agreement that emerged from his June 12 summit with Kim that had few details on how Pyongyang would surrender its nuclear weapons and ballistic missiles.
Although Trump said last week that North Korea was in the process of returning the remains of US troops missing from the 1950-1953 Korean War, Pompeo said none had yet been handed over to the United States.
He said he was optimistic the United States would begin receiving remains "in the not-too-distant future."
Pompeo also said he had seen "a modest amount" of backsliding from China on enforcing sanctions on North Korea.
Donald Trump gives the North Korea leader Kim Jong-un a thumbs up at their historic meeting on Sentosa Island. Source: AAP
"It is the set case that we have observed China not enforcing control over their cross-border areas as vigorously as they were six or 12 months ago," he said, but said that was in comparison to what had been an all-time high.
Pompeo was also questioned about Trump's saying after the summit with Kim that North Korea no longer posed a nuclear threat, an assertion questioned by analysts and mocked by Democrats.
Pompeo defended the statement, saying Trump had reduced the threat, by reducing tensions. "I think his point was a fair one.
For the moment, we have reduced risk," Pompeo told the subcommittee.
