At a joint news conference with visiting Japanese Prime Minister Shinzo Abe on Wednesday, President Donald Trump said the United States is “fighting very diligently” to secure the freedom of three Americans held by North Korea.

A senior administration official confirmed that CIA Director and Secretary of State nominee Mike Pompeo discussed the issue with North Korean dictator Kim Jong-un during their secret meeting over Easter weekend.

“I think there’s a good chance of doing it. We’re having very good dialogue,” Trump said.

The president said during the same press conference that he is prepared to “respectfully leave the meeting” with Kim if his summit with the North Korean leader is not “fruitful.” He did not specify whether the fate of the imprisoned Americans could be a deal-breaker.

Trump also promised to work for the freedom of Japanese citizens abducted by North Korea, saying their fate is “one of the truly most important things on Shinzo’s mind.”

The North Koreans have admitted to kidnapping 13 Japanese citizens, of whom five have been returned to Japan, while eight others died in captivity. Japan says four more of its citizens remain unaccounted for.

The three Americans still held by North Korea after the release and subsequent death of college student Otto Warmbier in June 2017 include Tony Kim and Kim Hak-song, both teachers at the unusual Christian-founded private school known as the Pyongyang University of Science and Technology, and Kim Dong-chul, who has been described as a Christian missionary.

Kim Dong-chul has been in captivity the longest since his arrest in October 2015. The North Koreans forced him to make a confession in which he claimed to be a paid espionage agent working for the South Korean government. Kim Hak-song and Tony Kim were vaguely charged with working to undermine the North Korean state.

Former Amnesty International executive Frank Jannuzi, who has experience working with North Korean diplomats, told the UK Express in March that he would “not be surprised” if North Korea released the three American prisoners as a goodwill gesture ahead of the Trump-Kim summit.

“The North Koreans have studied Donald Trump very carefully since he was elected in 2016. We have to remember that these three are of no strategic relevance at all. They know that to release them would allow him to claim a victory. It would put him in a good mood, basically,” Jannuzi contended.

Former Deputy Assistant Secretary of Defense for East Asia Abraham Denmark, now director of the Asia program at the Wilson International Center for Scholars, told Germany’s Deutsche Welle on Wednesday that he was mildly surprised Pompeo did not return from his Easter meeting with the three captive Americans in tow.

“I believe that it is impossible to negotiate with North Korea while there are American prisoners in the country. I believe releasing them in relatively good condition should be a precondition for talks. It is unclear how the administration is approaching this,” Denmark said.