"But we're talking right now".
Pompeo also touched on an issue that was once central to the administration's campaign of "maximum pressure" on North Korea, but has been rarely mentioned by USA officials since Trump agreed to the summit: human rights.
Mr Trump said "there's a very substantial chance" that the meeting will not take place on June 12.
"Even if sanctions are lifted, it may take time for North Korea (DPRK) to realize the economic benefits President Trump has suggested as it will need to make internal reforms before we are likely to see significant investment from the private sector", he said.
"We will apply financial pressure, coordinate with our (Department of Defense) colleagues on deterrence efforts, support the Iranian people, and hold out the prospect of a new deal for Iran - if it changes its behavior", Pompeo said Wednesday.
His aides are looking to Moon to help determine whether Kim is taking a harder line against denuclearisation than South Korea had previously communicated to them, a United States official said, speaking on condition of anonymity.
A satellite image provided by DigitalGlobe shows the nuclear test site in Punggye-ri, North Korea.
Trump expressed suspicion that the North's recent aggressive barbs were influenced by Kim's unannounced trip to China two weeks ago - his second in as many months.
"There are certain conditions that we want".
Travel will involve an 11-hour train ride, a four-hour bus journey and then a hike of another hour, a reporter with Russia's RT said on Twitter.
The North announced earlier this month that it planned to "completely" destroy the Punggye-ri facility in the country's mountainous northeast.
FILE - In this September 9, 2016 file photo, a man watches a TV news program reporting North Korea's nuclear test at Seoul Railway Station in Seoul, South Korea.
Hawaii volcano spews 6 mile-high plume of ash, could blow again
The crater sits within Hawaii Volcanoes National Park, which has been closed since May 11 in preparation for an eruption. Earthquakes continue to shake the Big Island, with the most severe at around 8:30 a.m. producing a 4.4 magnitude quake.
The newspaper reiterated harsh criticism against Max Thunder, denouncing the exercise as a practice for a pre-emptive airstrike.
Asked whether there has been a breakthrough between the two Koreas, a Cheong Wa Dae official said while they could not reveal the details, there are "various analyses" that have convinced Moon that the talks would resume.
The government hopes to build up the tourism industry of a city once most famous for being the launch site of many of North Korea's intercontinental ballistic missiles (ICBMs). The eight South Koreans arrived in Wonsan on Wednesday, where they were forced to leave their radiation detectors, satellite phones and Bluetooth mouses before they all set off for the test site, according to South Korean media pool reports.
Observers will be watching the nuclear test site destruction ceremony closely for any clues to the North's mood.
But there has been increasing pessimism about the meeting after North Korea scrapped the inter-Korean talks and threatened to do the same for the Kim-Trump summit in protest of the South Korea-U.S. military drills and what it calls Washington's push for "one-sided" disarmament.
For his part, Moon tried to disperse the US skepticism regarding the Trump-Kim meeting.
It has said in previous, failed talks that it could consider giving up its arsenal if the United States provided security guarantees by removing its troops from South Korea and withdrew its so-called nuclear umbrella of deterrence from South Korea and Japan.
"I'm very hopeful that that meeting will take place".
"Thanks to your vision of achieving peace through strength, as well as your strong leadership, we're looking forward to the first-ever US-North Korea summit", Moon said in an opening statement directed at Trump.
When they sat down in the Oval Office, President Trump said he believes Kim Jong Un is serious about denuclearization.