Washington (CNN) US Secretary of State Mike Pompeo arrived in Pyongyang Wednesday local time to continue preparations for President Donald Trump's upcoming summit with North Korean leader Kim Jong Un .

A South Korean government official told reporters in Tokyo Wednesday he expects Pompeo to leave Pyongyang with three American detainees who have been held in North Korea for months

The official said the date and location of the Trump-Kim summit will also likely be announced following Pompeo's trip.

"The location is picked, the time and date, everything is picked and we look forward to having a great success," Trump said Tuesday at the White House.

Pompeo also tweeted about the trip on Tuesday.

"Headed back to #DPRK at the invitation of the North Korean leadership. I look forward to planning a successful summit between President Trump and Kim Jong-un," Pompeo tweeted.

Headed back to #DPRK at the invitation of the North Korean leadership. I look forward to planning a successful summit between President Trump and Kim Jong-un. — Secretary Pompeo (@SecPompeo) May 8, 2018

Asked whether Pompeo would return with the three American prisoners currently held in North Korea, Trump played coy.

"We'll all soon be finding out," he said. "It would be a great thing if they are."

Speaking to reporters traveling with him to North Korea, Pompeo said that while he will raise the plight of the three detained US citizens on his trip, and he hopes North Korea will "do the right thing," the regime has not committed to their release.

"We've been asking for the release of these detainees for 17 months," he said. "We'll talk about it again. It'd be a great gesture if they'd agree to do so."

Pompeo previously traveled to North Korea over the Easter weekend, where he met with the North Korean leader. On Tuesday, he said this trip will allow him to continue discussions he began on his last visit and begin to outline the substance of an agenda for the summit between Trump and Kim.

"The second piece is, we also want to make sure what our expectations are not," said Pompeo, aboard a C-32A. "We are not going to head down the path we headed down before."

"We will not relieve sanctions until such time as we have achieved our objectives," he added. "We're not going to do this in small increments, where the world is coerced into relieving economic pressures."

Pompeo said he hopes the two countries can outline a set of conditions that will allow for a change in their security relationship, as well as pin down the specific details for the summit itself, including date, location and duration.

He also told the reporters he doesn't know exactly who he will meet in North Korea.

"We're prepared to meet anyone who can speak on behalf of the North Korean government and give us solid answers so we're prepared," he said.

Separately, a senior State Department official told the reporters traveling with Pompeo the US "will be listening for signs from North Korea that things have substantially changed since Kim declared on New Year's Eve that he would mass produce nuclear warheads and the means to deliver them."

"Only a year ago," the official noted, "he used chemical weapons to assassinate his half-brother."

The official said Pompeo is "clear-eyed about not repeating the mistakes of the past," and that what's needed is a "new and bold approach."

"We are looking for bold steps," said the official. "Anything less would be repeating the mistakes of the past."

"We are not going to fall for theatrical pronouncements on the end of their nuclear program," the official added. "That is not convincing evidence of dismantling their nuclear program. It wasn't then, and it won't be now."

Past efforts, "however well intentioned, have not addressed the North Korean threat to our security interests."

Accompanying Pompeo on the trip are Brian Hook, the head of the State Department's policy planning team, as well as Matt Pottinger from the National Security Council.

Lisa Kenna of the executive secretariat and acting Undersecretary of State for Public Diplomacy Heather Nauert are also traveling with the secretary.