"Nothing has changed," Pompeo told a news conference after a meeting with Japan's foreign and defense ministers. "We continue to work."

"Still in charge of the team," he said.

North Korea this week demanded that Pompeo be excluded from future talks after he apparently encouraged President Donald Trump to stand firm during a summit in Hanoi with North Korean leader Kim Jong Un.

Trump has spoken fondly of his relationship with the young authoritarian leader and last month said he had blocked the imposition of punishing new sanctions on the cash-strapped country, despite Pompeo's vows to maintain strong pressure.

"President Trump is obviously in charge of the overall effort but my team, Special Representative (Steve) Biegun, will continue to lead the US effort" to ensure Kim does as he promised, Pompeo said.

"I'm convinced we'll still have a real opportunity to achieve that outcome and our diplomatic team will continue to remain in the lead," he said.

Pompeo traveled four times last year to Pyongyang and has said that Kim has committed in general terms to giving up his nuclear program as part of a deal with the United States.