On the eve of a historic summit between President Donald Trump and Kim Jong Un, Pompeo sounded an upbeat tone, saying that preparatory talks were advancing more quickly than expected.

Stating that the United States would not again be duped by North Korea, Pompeo said the Trump administration would only accept complete denuclearisation.

In return, he said, "we will take actions to provide them sufficient certainty that they can be comfortable that denuclearisation is not something that ends badly for them," Pompeo said.

"Just the opposite. That it leads to a brighter and better future for the North Korean people."

Pompeo said these guarantees would be "different and unique" than America has been willing to provide before.

"I'm very optimistic we will have a successful outcome with the two leaders," he said.

"There are only two people that can make decisions of this magnitude. Those two people will sit in a room tomorrow."