U.S. Secretary of State Mike Pompeo said Wednesday that he hopes to announce the date and venue for a meeting between U.S. President Donald Trump and North Korean leader Kim Jong-un early next week, Yonhap News reported.

En route home from a meeting with Kim in Pyongyang, Pompeo said the date, time and location have all been fixed for the unprecedented summit.

"We hope in the next handful of days, we'll be able to announce the location and the date and time," he told reporters on a plane to Japan, according to a transcript released by his office. "We're hoping the beginning of next week."

The Trump-Kim meeting is expected to be a one-day event, but it could extend into a second day if there is more to discuss.

Defense Secretary Jim Mattis told Congress on Wednesday there's “reason for optimism” on the Trump administration’s efforts to denuclearize the Korean Peninsula after the release of three American prisoners from North Korea“

“For right now, Secretary Pompeo is airborne bringing home the three released American citizens as we speak,” Mattis told the panel. “And I think there is reason for some optimism that these talks could be fruitful.”