The two, along with fellow detainee Kim Dong-chul, were granted "amnesty" by Pyongyang following a meeting between Secretary of State Mike Pompeo and North Korean leader Kim Jong Un, and landed back in the United States on Thursday, to be welcomed by President Donald Trump.
Coates said that North Korea handing over details about its existing programme would "set us up with a greater chance of success, anything that they would like to do, but we haven't been signaling preconditions up until this point".
But former spy chief Kim Yong Chul, director of North Korea's United Front Department, said in a toast to Pompeo over lunch in Pyongyang: "We have perfected our nuclear capability". He was captured trying to return to his home in Dandong, China, in May a year ago.
"And that's what he's going to be seeking", White House Deputy Press Secretary Raj Shah told reporters aboard the Air Force One travelling to Indiana.
Kim Dong-chul was arrested on suspicion of espionage in 2015, while Kim Hak-song and Tony Kim, who had worked at Pyongyang University of Science and Technology, were detained a year ago. "Me, I had to do a lot of labor, but when I got sick, I was also treated by them".
So far, the North Korean regime has made vague pledges to "denuclearize" but not said spelled out what that means, when it would happen or how it would be implemented.
On May 9, Trump announces the three men are headed to the United States, personally welcoming them to Washington, offering effusive thanks to Kim and heralding a diplomatic victory.
Meanwhile, US Vice President Mike Pence revealed details about the conditions of the three Americans, saying one was evidently kept from the daylight.
Joking with reporters, Trump said the three men's arrivals had probably broken "the all time in history television rating for three in the morning".
Presidente asistirá mañana al traspaso de mando Costa Rica
Así mismo, aprovechará su estancia para visitar la sede de la Corte Interamericana de Derechos Humanos (Corte IDH), también ubicada en la capital costarricense.
Such a move might force U.S. to halt the meeting, a presidential spokesman said yesterday.
Trump has pushed countries around the world to cut diplomatic and economic ties to Pyongyang as part of his "maximum pressure" strategy. "They take great pride in being a friend to all".
The three former detainees issued a joint statement on Wednesday thanking Trump for their release.
"We can not forget: No regime has the right to hold American citizens in captivity without cause, and under no circumstances should American citizens be viewed as bargaining chips". Welcome home from your frightening ordeal in North Korea.
Kim Jong Un has simply demonstrated he's serious about sitting down with Trump. More than a dozen abductees still remain missing, according to the Japanese government.
Trump is leaning toward holding the meeting in Singapore, according to an administration official, who asked not to be named as the decision hasn't been finalized. Moon is scheduled to visit the White House on May 22 to debrief Trump on his own meeting with Kim and discuss strategy ahead of Trump's summit.
It was their second encounter in less than six weeks to prepare the first-ever meeting between sitting US and North Korean leaders.
Singapore had emerged as the likely host of the summit after Mr Trump yielded to the concerns of his aides and backed off his desire to hold the meeting at the inter-Korean Demilitarised Zone.
Trump said he will not disclose whether he will have any personal conversations with Kim as they prepare for their historic summit in the coming weeks.