U.S. Secretary of State-designate Mike Pompeo voiced cautious optimism in President Donald Trump's ability to negotiate a nuclear deal with Pyongyang, but also struck a tone on the issue that was likely to trigger concern in Tokyo and Seoul, during a Senate confirmation hearing Thursday.

Pompeo, who currently serves as CIA chief, told the hearing that the summit between Trump and North Korean leader Kim Jong Un, planned for May or early June, would lay the foundations for denuclearizing the North.

Referring to what would be the first direct engagement between a sitting U.S. president and a North Korean leader, Pompeo played down expectations of a "comprehensive agreement" in just a single meeting.