CIA director Mike Pompeo has defended Donald Trump's decision to meet North Korean leader Kim Jong-un, saying the president understands the risks. Mr Trump "isn't doing this for theatre, he is going there to solve a problem," the spy chief told Fox News Sunday.
The president has said the yet-to-be-arranged summit could produce the "greatest deal for the world". But critics have warned that if the talks go poorly, the two nations will be in a worse position than before.
No sitting US president has ever met a North Korean leader.
Such a summit, which Pyongyang has long wanted, has previously been seen as possible only after major concessions from the North Koreans.
But Mr Trump reportedly accepted the offer on the spot when it was relayed by South Korean envoys on Thursday, taking his own administration by surprise.
North Korea has said several times in the past that it would consider giving up its nuclear weapons under the right conditions.
But attempts to negotiate aid-for-disarmament deals have failed repeatedly since 2003, when the North pulled out of the Nuclear Non-Proliferation Treaty (NPT).
Mr Pompeo told CBS the administration had its eyes "wide open" to the challenge of dealing with North Korea.
He said the country was coming to the table now because US-led sanctions have battered it economically.
"Never before have we had the North Koreans in a position where their economy was at such risk, where their leadership was under such pressure," he told Fox News.
Another top White House official, Treasury Secretary Steve Mnuchin, stressed the "clear" objective of the talks was getting rid of nuclear weapons on the Korean peninsula, and restated that the US expects there to be no missile or nuclear test ahead of the meeting.
Fears Kim could 'take advantage'
Politicians from both main parties in US politics expressed concerns over the planned meeting, however.
Republican Senator Cory Gardner told CBS he wanted "concrete, verifiable steps toward denuclearisation" before the talks take place.
Another Republican Senator, Jeff Flake, told NBC he was sceptical about whether denuclearisation was a realistic goal at all.
Speaking to the same channel, Democratic Senator Elizabeth Warren raised fears that what she called the "decimated" US State Department lacked officials familiar with Pyongyang's methods.
"I want to see our president succeed, because if he succeeds, America succeeds. The world is safer," she said.
"But I am very worried that they're going to take advantage of him."
Trump: North Korea 'wants peace'
At a political rally in Pennsylvania on Saturday, Mr Trump told supporters he believed North Korea wanted to "make peace".
But he said he might leave the talks quickly if it didn't look like progress for nuclear disarmament could be made.
"Hey, who knows what's going to happen?" said Mr Trump at the rally for a Republican congressional candidate. "I may leave fast or we may sit down and make the greatest deal for the world."
He said he hoped a deal to ease nuclear tensions would happen, particularly to help countries like North Korea.
No date or place has been set for the meeting, despite initial reports it would happen by the end of May.
South Korea's presidential office said the North Korean truce village of Panmunjom, which sits at the demilitarised zone between the North and the South, was a "serious" option, Yonhap news agency reported.
Sweden, Switzerland and China have also been named as possible hosts.