Sanders says, "All Americans look forward to welcoming them home and to seeing them reunited with their loved ones".
They are Korean-American missionary Kim Dong-chul, detained in 2015; Kim Sang-duk, also known as Tony Kim, who spent a month teaching at the foreign-funded Pyongyang University of Science and Technology (PUST) before he was arrested in 2017; and Kim Hak-song, who also taught at PUST and was detained a year ago.
The new secretary of State was on his second trip to North Korea this year to meet with Kim in preparation for the summit with Trump.
North Korea official Kim Yong Chul, who met Pompeo in Pyongyang, insisted the country's openness to talks was "not the result of sanctions that have been imposed from outside", but a change in regime focus.
"We'll see how it all works out", Trump said Tuesday.
Attorney General Jeff Sessions to Visit US-Mexico Border in San Diego
On Monday, Sessions said the Trump administration's actions were necessary because of "massive increases in illegal crossings in recent months".
Kim also noted improved relations between North and South Korea and pushed back against the idea that US pressure led to the likely summit. He died days later.
Kim Dong-chul and Tony Kim were both born in South Korea, while Kim Hak-song is believed to have been born in China, although he is ethnically Korean.
"There is reason for some optimism that these talks could be fruitful", U.S. Defense Secretary Jim Mattis said of the coming summit. South Koreans typically hyphenate their first names - for example, South Korean president Moon Jae-in - while North Koreans do not, such as in the case of Kim Jong Un.
He also disclosed that Pompeo had set the stage for his meeting with Kim Jong Un, including a date and place he did not fully reveal, after a "good meeting" with the North Korean dictator.
Kim also expressed hope that the U.S. and North Korea would take "phased and synchronous measures", signalling Pyongyang wanted a quid pro quo. Shortly afterward, the White House released photographs of Pompeo and Kim. He did not confirm whether he'd be traveling home with the three American citizens now detained in North Korea.
The upbeat announcements on the North Korea front came just hours after it was revealed that Trump's personal lawyer Michael Cohen received, into a business account he controlled, $ 500,000 from a Russian oligarch with close ties to Vladimir Putin. He was later sentenced to 15 years hard labor for allegedly stealing a propaganda banner at his hotel. He was working as an accounting professor at Pyongyang University of Science and Technology when he was detained.
"So everything is going well in Pyongyang now", he said, adding that from now on, North Korea would be concentrating all its efforts "into the economic progress of our country". That contradicted Trump, who has said repeatedly that his pressure tactics brought North Korea to the negotiating table.
The historic summit between the leaders of North and South Korea has whetted the former's appetite for investments from the U.S., according to a South Korean official, as quoted by the Daily Express.
Asked whether a summit with Kim would be possible while Americans languish in North Korean jails, he replied.