The US hopes to see “major disarmament” by North Korea by the end of 2020, Secretary of State Mike Pompeo says.
His comments come a day after an unprecedented meeting between President Donald Trump and North Korean leader Kim Jong-un in Singapore.
In a statement North Korea agreed to work towards “complete denuclearisation of the Korean Peninsula”.
But the document has been criticised for lacking details on when or how Pyongyang would give up its weapons.
Speaking in South Korea, where he discussed the outcome of the summit, Secretary Pompeo said there was still “a great deal of work to do” with North Korea.
But he added: “Major disarmament… We’re hopeful that we can achieve that in the two and half years.”
He said he was confident Pyongyang understood the need for verification that it was dismantling its nuclear programme.
His comments come after President Trump declared that North Korea was no longer a nuclear threat, insisting “everybody can now feel much safer”.
The credibility of that claim is in doubt. That is because under the deal, the North retains its nuclear warheads, the missiles to launch them and has not agreed to any specific process to get rid of them.
Pyongyang has celebrated the summit as a great win for the country.