A high-stakes second meeting to strike a nuclear disarmament deal between the North's leader Kim Jong Un and Trump broke up in disarray Thursday, without even a joint statement.

But Bolton told CBS's "Face the Nation" Trump's failure in getting commitments from Pyongyang on destroying its nuclear capability should be seen as "a success, defined as the president protecting and advancing American national interests."

The White House aide said the issue was whether North Korea would accept what the president called "the big deal" -- denuclearizing completely or something less, "which was unacceptable to us."

"So the president held firm to his view. He deepened his relationship with Kim Jong Un. I don't view it as a failure at all when American national interests are protected."

The outcome in Hanoi fell far short of the pre-meeting expectations, after critics said their initial historic meeting in Singapore -- which produced only a vague commitment from Kim to work "toward complete denuclearization of the Korean peninsula" -- was more style over substance.

Others pointed to a lack of preparation, with the two sides unable to bridge the gaps between them in time.

According to senior US officials, in the week leading up to the Hanoi summit the North Koreans had demanded the lifting of effectively all the UN Security Council economic sanctions imposed on Pyongyang since March 2016.

- 'Barbaric and unacceptable' -

In return, Pyongyang was only offering to close a portion of the Yongbyon complex, a sprawling site covering multiple different facilities -- and the North is believed to have other uranium enrichment plants.

"Sometimes you have to walk and this was just one of those times," an unusually downcast Trump told reporters on Thursday, adding that he would "rather do it right than do it fast."

After returning to Washington, the US president tweeted Friday that his relations with Kim were "very good".

"What President Trump was trying to do was look at what was possible for them overall," Bolton told CBS.

"He remains optimistic this is possible. Kim Jong Un himself said in our last meeting, you know, we're going to go through many stations before we achieve this deal. The meeting in Hanoi was one such station."

Bolton repeated the US position that it would help North Korea's economic progress if it committed to complete denuclearization and closing its chemical and biological weapons programs.

Compounding criticism of the summit, Trump sparked a firestorm by his remarks on the case of an American student tortured and left in a coma in North Korea.

The president said he believed Kim's claim that he didn't know what happened to 22-year-old Otto Warmbier, who died days after being sent back to the United States in 2017.

After a stern rebuke from Warmbier's parents, Trump took to Twitter, insisting he held North Korea responsible for the student's death -- but without directly blaming Kim or even mentioning him.

"The president's been very clear he viewed what happened to Otto Warmbier as barbaric and unacceptable," Bolton told CBS.

"And I think the best thing North Korea could do right now would be to come up with a full explanation of exactly what happened to him."

ft/jm

CBS CORPORATION