National security adviser John Bolton on Sunday declared that President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE’s summit with North Korean leader Kim Jong Un, which ended without an agreement between the two sides, was a "success."

“I think it was unquestionably a success for the United States because the president protected, defended American interests,” Bolton said on CNN’s “State of the Union.”

Bolton appeared on a trio of Sunday talk shows, where he downplayed concerns that the U.S. failed to get something out of the latest round of talks.

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Bolton said on CBS's "Face the Nation" that there’s “no expiration date” for the Trump administration’s push to rid North Korea of its nuclear arsenal. He acknowledged, however, that Pyongyang has not committed to abandoning its nuclear weapons.

“I think [Trump] remains optimistic that this is possible,” Bolton said on CBS.

"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. So the president is ready to keep talking."

Trump last week ended his two-day summit with Kim abruptly without signing any type of agreement as the two sides had during the leaders' first meeting last year.

Trump later said he had to “walk away” from the second summit after North Korea asked for all sanctions to be lifted, but North Korean officials disputed that account and said they only asked for relief from some sanctions.

Bolton on Sunday rejected labeling the summit a failure, arguing that it was better to leave with no deal than a bad deal. He also pushed back on the suggestion that Trump had helped legitimize Kim on the world stage.

“The president’s view is he gave nothing away,” Bolton said on CBS.

He also credited sanctions with bringing North Korea to the negotiating table, and noted that those penalties will remain in place.

"It was the sanctions that brought the North Koreans to the table," Bolton said. "It's the sanctions they want relief from and relief they can get if they denuclearize."

The national security adviser was pressed in each of his Sunday show appearances on the president's comments that he took Kim's word that the North Korean leader was unaware of the imprisonment and treatment of American student Otto Warmbier.

Trump's remarks on Warmbier, who was imprisoned in North Korea in 2016 and died shortly after returning to the U.S. in 2017, sparked bipartisan backlash. The president later claimed he was "misinterpreted," but did not say he held Kim responsible for Warmbier's death.

On "Fox News Sunday," Bolton sought to explain that the president taking Kim's word "doesn’t mean that he accepts it as reality." He added that Trump considers Warmbier's death to be "barbaric."

Bolton demurred on CNN when asked if he personally took Kim at his word.

“My opinion doesn’t matter," Bolton said.

Updated at 10:30 a.m.